Solid state sensor

Abstract

Solid state sensors for measuring various physical parameters are described herein. Solid state sensors may be used in systems, devices, and methods for controlling blood flow or for measuring (e.g., monitoring) blood pressure. In some examples, a method may include obtaining a first count number indicative of a number of oscillations at a first ring oscillator circuit during a sampling period. The first ring oscillator circuit may be associated with the sensor and oscillate at a first oscillation rate. The first oscillation rate may be based on a first set of physical parameters and a second physical parameter. The method may also include obtaining a second count number indicative of a number of oscillations at the second ring oscillator circuit during the sampling period. The second ring oscillator circuit may be associated with the sensor and oscillate at a second oscillation rate. The second oscillation rate may be based on the first physical parameter but not the second physical parameter. The method may also include determining a value associated with a second physical parameter at the sensor based on the first count number and the second count number.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 63 / 346,286, filed on May 26, 2022, which is hereby incorporated by reference in its entirety. Technical Field

[0003] The devices, systems, and methods herein relate to sensors that can be used to measure parameters including, but not limited to, pressure. Background Art

[0004] The sensor can be configured to measure various physical properties. For example, a Wheatstone bridge sensor may include a piezoresistive circuit on a silicon-based die and may be configured as a pressure sensor or a strain gauge. However, piezoresistive sensor measurements are affected by inherent resistor offsets and inherent temperature offsets, which may be mitigated by an offset compensation circuit, which may include one or more of a differential amplifier, a potentiometer, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), a resistor, etc. In addition, the wires coupling the sensor to the electronic circuit may have a length (e.g., 500 mm or greater) that serves as an antenna for picking up common-mode noise. Differential low-pass filters and differential amplifiers may be used to provide high common-mode rejection for the wires. The circuits required to compensate for sensor offsets and wire noise increase the cost, size, weight, and manufacturing complexity of the sensor. Therefore, additional devices, systems, and methods for measuring parameters may be desirable. Summary of the invention

[0005] Described herein are systems, devices, and methods including sensors that can be used to measure one or more parameters (e.g., physical properties), including, but not limited to, pressure (e.g., blood pressure). In some variations, the sensor can be part of a device that controls blood flow, for example, as one or more of a sensor proximal to an expandable member (e.g., a balloon), a sensor distal to an expandable member, and a sensor within the expandable member. In other variations, the sensor can be included in a device that measures pressure (e.g., blood pressure) without controlling blood flow. One or more sensors can be used to measure the one or more parameters. For example, multiple sensors (e.g., two, three, four, or more sensors) can be used to measure the same parameter, each of the multiple sensors can be used to measure a different parameter, or multiple sensors can be used, wherein some of the multiple sensors can be used to measure the same parameter, and some of the multiple sensors can be used to measure different parameters. Each sensor can be housed in its own sensor housing, or multiple sensors can be housed in a single sensor housing. In some variations, a sensor housing that houses one or more sensors can be integrated into an elongated body (e.g., a catheter), as described in more detail herein. In one embodiment, the sensor may include: a first circuit configured to receive an input clock signal and output a first output clock signal using an adjustable delay, the first output clock signal having a predetermined ratio between the input clock signal and the first output clock signal; a second circuit configured to receive the input clock signal and output a second output clock signal using the adjustable delay; and a third circuit coupled to the first circuit and the second circuit, the third circuit configured to generate a third signal based on a difference between the first output clock signal and the second output clock signal.

[0006] In some variations, the first output clock signal may vary based on a first set of parameters, and the second output clock signal may vary based on a second set of parameters different from the first set of parameters. In some of these variations, the first set of parameters may include one or more of temperature and voltage. In some of these variations, the second set of parameters includes temperature, voltage, and one or more of: force, pressure, light amplitude, audio amplitude, and resistance or capacitance corresponding to a chemical or physical reaction.

[0007] In some variations, the third signal may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude. In some variations, the frequency of the first output clock signal and the frequency of the second output clock signal may each be greater than the frequency of the input clock signal. In some variations, the first circuit may include a first plurality of delay circuits arranged in a ring configuration. In some of these variations, the first plurality of delay circuits may include a first plurality of inverter circuits and a first adjustable delay circuit. In some of these variations, the first adjustable delay circuit may include a rate counter. In some of these variations, the first plurality of inverter circuits may be coupled to a first multiplexer. In some of these variations, the first plurality of inverter circuits may have a closed-loop configuration with positive feedback.

[0008] In some variations, the first delay circuit may include a first resistor-capacitor delay circuit. In some variations, the second circuit may include one or more of a resistor-capacitor delay circuit, a resistor-inductor delay circuit, and a capacitive delay circuit. In some variations, the first circuit may include a first oscillator circuit.

[0009] In some variations, a fourth circuit may be coupled to the third circuit, the fourth circuit being configured to receive the input clock signal and output a fourth output clock signal using the adjustable delay. The third circuit may be configured to generate a fifth signal based on a difference between the first output clock signal and the fourth output clock signal. In some of these variations, the fifth signal may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.

[0010] In some variations, the substrate may include the first circuit, the second circuit, and the third circuit. In some variations, the first substrate may include one of the first circuit and the second circuit, and the second substrate may include the other of the first circuit and the second circuit.

[0011] In some variations, the fourth circuit may be configured to output the third signal as a digital signal. In some variations, the fourth circuit may be configured to output the third signal as a set of binary coded bits at a periodic rate. In some variations, the fourth circuit may include one or more of a wire and an antenna.

[0012] The present invention also describes a method for measuring a parameter, the method comprising: receiving an input clock signal; using an adjustable delay to generate a first output clock signal, the first output clock signal having a predetermined ratio between the input clock signal and the first output clock signal; using the adjustable delay to generate a second output clock signal; and generating a third signal based on a difference between the first output clock signal and the second output clock signal.

[0013] In some variations, the first output clock signal may be varied based on a first set of parameters, and the second output clock signal may be varied based on a second set of parameters different from the first set of parameters. In some variations, the first set of parameters may include one or more of temperature and voltage. In some variations, the second set of parameters includes temperature, voltage, and one or more of: force, pressure, light amplitude, audio amplitude, and resistance or capacitance corresponding to a chemical or physical reaction.

[0014] In some variations, the third signal may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude. In some variations, the frequency of the first output clock signal and the frequency of the second output clock signal may each be greater than the frequency of the input clock signal.

[0015] In some variations, the adjustable delay may be used to generate a fourth output clock signal, and a fifth signal may be generated based on a difference between the first output clock signal and the fourth output clock signal. In some variations, the fifth signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.

[0016] In some variations, the third signal may be output as a digital signal. In some variations, the third signal may be output as a set of binary coded bits at a periodic rate.

[0017] A sensor is also described herein, the sensor comprising a first ring oscillator circuit that oscillates at a first oscillation rate. The first oscillation rate may be based on a first set of physical parameters and a second physical parameter. The sensor may also include a second ring oscillator circuit that oscillates at a second oscillation rate. The second oscillation rate may be based on the first physical parameter but not on the second physical parameter. The sensor may also include a first rate counter circuit that is operatively coupled to the first ring oscillator circuit and configured to count a first number of oscillations at the first ring oscillator circuit during a sampling period. The sensor may also include a second rate counter circuit that is operatively coupled to the second ring oscillator circuit and configured to count a second number of oscillations at the second ring oscillator circuit during the sampling period. The sensor may also include a circuit system that is configured to receive a representation of the first number of oscillations and a representation of the second number of oscillations, and in response to receiving the representation of the first number of oscillations and the representation of the second number of oscillations, generate a value associated with the second physical parameter at the sensor based on the first number of oscillations and the second number of oscillations.

[0018] A sensor is also described herein. The sensor includes a first ring oscillator circuit that oscillates at a first oscillation rate. The first oscillation rate may be based on a first set of physical parameters and a second physical parameter. The sensor may also include a second ring oscillator circuit that oscillates at a second oscillation rate. The second oscillation rate may be based on the first physical parameter but not on the second physical parameter. The sensor may also include a first rate counter circuit that is operatively coupled to the first ring oscillator circuit and is configured to count a first number of oscillations at the first ring oscillator circuit during a sampling period. The sensor may also include a second rate counter circuit that is operatively coupled to the second ring oscillator circuit and is configured to count a second number of oscillations at the second ring oscillator circuit during the sampling period. The sensor may also include a communication circuit system configured to transmit the representation of the first oscillation quantity and the representation of the second oscillation quantity to a processing circuit system operatively coupled to the communication circuit system, so that the processing circuit system generates a value associated with the second physical parameter at the sensor based on the first oscillation quantity and the second oscillation quantity in response to receiving the representation of the first oscillation quantity and the representation of the second oscillation quantity from the communication circuit system.

[0019] A method is also described herein that may include obtaining a first count number indicating a number of oscillations at a first ring oscillator circuit during a sampling period. The first ring oscillator circuit may be associated with a sensor and oscillate at a first oscillation rate. The first oscillation rate may be based on a first set of physical parameters and a second physical parameter. The method may also include obtaining a second count number indicating a number of oscillations at a second ring oscillator circuit during the sampling period. The second ring oscillator circuit may be associated with the sensor and oscillate at a second oscillation rate. The second oscillation rate may be based on the first physical parameter and independent of the second physical parameter. The method may also include determining a value associated with the second physical parameter at the sensor based on the first count number and the second count number.

[0020] A method is also described herein that may include: measuring a first value of a first parameter using a first sensor, transmitting the first value to a second sensor coupled to the first sensor, and measuring a second value of a second parameter using the second sensor. The method may also include: generating a sequence value including the first value and the second value.

[0021] Also described herein is a device configured to monitor the physiological condition of a patient or adjust a physiological parameter (e.g., blood flow or blood pressure) of the patient. These devices may include any one or more of the sensors described herein integrated into an elongated body (e.g., a catheter). In some variations, the one or more sensors may be configured to measure blood pressure. When the sensor is included in a blood flow control device, the balloon may be coupled to the elongated body and configured to be placed in a blood vessel. The one or more sensors may be housed in a sensor housing that protects the sensor from damage caused by pressurization of body fluids (e.g., blood) or balloons from a blood flow control device. The sensor housing may be formed of any suitable material such as a polymer, a metal, or a metal alloy. In some variations, the sensor housing is made of stainless steel. In other variations, the sensor may be fully or partially encapsulated in the polymer in the sensor housing.

[0022] Additionally, the present invention also describes a device configured to monitor blood pressure. The device may include any one or more sensors of the sensors described herein that measure blood pressure integrated into an elongated body (e.g., a catheter). The one or more sensors may be housed in a sensor housing, as described above, to help protect the sensor from damage caused by body fluids (e.g., blood) or other external factors. In some variations, the sensor and / or the sensor housing may be tubular in shape and have a diameter of about 1 Fr. The sensor may be fully or partially encapsulated in the sensor housing in the polymer. When the sensor is coupled to a PCBA (printed circuit board assembly) housing, the housing may include an adhesive configured to attach the PCBA housing to the patient's skin. In some cases, the adhesive may be provided as an adhesive patch. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1A and Figure 1B is a schematic diagram of a conventional Wheatstone bridge sensor.

[0024] Figure 2A and Figure 2B It is a schematic block diagram of a conventional sensor.

[0025] Figure 3 is a schematic block diagram of an illustrative variation of a sensor system.

[0026] Figure 4 is a schematic diagram of an exemplary variation of an oscillator circuit.

[0027] Figure 5 is a schematic diagram of an illustrative variation of a sensor.

[0028] Figure 6 A flow chart representation of an illustrative variation of a method of measuring a parameter is depicted.

[0029] Fig. 7A , Figure 7B and Figure 7C is a schematic diagram of an exemplary variation of a sensor.

[0030] Figure 8 Exemplary variations of blood flow control devices comprising an elongated body with an integrated sensor are illustrated.

[0031] Fig. 9A and Fig. 9B Schematic diagrams of a first ring oscillator circuit and a second ring oscillator circuit are shown respectively.

[0032] Fig.10 A schematic diagram of a circuit combining two ring oscillator circuits is shown.

[0033] Fig.11A and Fig. 11B A schematic diagram of a circuit including a sensor chip and a microcontroller chip is shown.

[0034] Fig.12 A flow chart of an exemplary method of determining a value associated with a physical parameter of interest at a sensor is depicted.

[0035] Fig.13A and Fig. 13B An example of a latch serializer communicatively coupled to a plurality of counters and an example of a UART output from the latch serializer are shown respectively.

[0036] Fig.14A and Fig. 14B Shown are exemplary configurations of multiple sensors connected in series (eg, daisy-chained together) and a latch sequencer that receives bits from an upstream sensor to generate a sequence output measured by the connected sensors.

[0037] Fig.15 Top, perspective, side, and front views of exemplary variations of the chip are shown.

[0038] Fig.16 An exemplary block diagram of a sensor is shown.

[0039] 17A to 17C Perspective, top, and front views of a sensor coupled to an exemplary sensor housing are shown.

[0040] Fig.18 An exemplary sensor housing is shown including struts and cutouts to aid in attaching the sensor to the elongated body and / or sensor sleeve.

[0041] Fig.19 An exemplary variation of a sensor coupled to an elongated body using a sensor sleeve is shown.

[0042] Fig. 20A and Fig. 20B An exemplary view of a sensor housing within an elongated body is shown.

[0043] Fig.21 An exemplary blood flow control system including a sensor as described herein is illustrated.

[0044] FIG. 22A to FIG. 22C An exemplary pressure sensing device incorporating a sensor as described herein is shown. DETAILED DESCRIPTION

[0045] Described herein are systems, devices, and methods for measuring parameters (e.g., physical properties), including, but not limited to, temperature, voltage, force, pressure, light amplitude, and audio amplitude. For example, in some embodiments, the systems, devices, and methods described herein may include a sensor configured to measure a change in electrical propagation time (e.g., delay) corresponding to a physical property. The sensor may be coupled to a computing device (e.g., a microcontroller) configured to receive an output from the sensor, determine a measured value of the parameter, and optionally output (e.g., display) the measured value and / or send an indication of the measured value to another computing device. The sensor may be disposed within a sensor housing to help protect the sensor from fluid (e.g., blood) and / or from damage caused by other external elements. The sensor may be housed in a sensor housing, positioned within a sensor housing, and / or encapsulated in a sensor housing, and integrated into an elongated body (e.g., a catheter) used in various devices (e.g., blood flow control devices and pressure monitoring devices), as further described herein.

[0046] The systems, devices, and methods described herein inherently compensate for variations in temperature, voltage, silicon skew, common-mode noise, etc., and can be used in medical, automotive, aerospace, and industrial applications, especially those with size and / or weight constraints. In contrast, conventional PLL multipliers require complex analog modeling of silicon processes and are often problematic under specific combinations of temperature, voltage, and / or speed of the silicon. However, the systems, devices, and methods described herein do not require conventional compensation solutions, such as additional circuit elements including differential amplifiers, differential low-pass filters, offset compensation, and analog-to-digital converters (ADCs).

[0047] sensor

[0048] In general, the sensors described herein may include a plurality of compensating ring clock multipliers (e.g., oscillator ring circuits) configured to generate and output accurate higher-speed clock signals from lower-speed clock signals. An adjustable delay may be calculated for an output clock signal of a first oscillator ring circuit corresponding to a first set of parameters (e.g., temperature, voltage, silicon die). A second oscillator ring circuit may be configured to generate and output a second clock signal that changes the first set of parameters in response to at least one additional parameter (e.g., pressure). The difference between the output clock signals corresponds to a measurement of a sensed parameter (e.g., pressure) that inherently compensates for the first set of parameters (e.g., temperature, voltage, silicon die). Additional oscillator ring circuits may be used to measure additional parameters. Furthermore, in some variations, the measured parameters may be output as digital signals, which may increase immunity to electrostatic discharge.

[0049] Figure 1A , Figure 1B , Figure 2A and Figure 2B Conventional sensors are illustrated along with their various limitations and disadvantages relative to the invention described herein. Figure 1A is a schematic diagram of a conventional Wheatstone bridge sensor 100 (eg, a pressure sensor, a strain gauge) including resistors R1, R2, R3, and R4 coupled to a voltage source V and a voltage measurement circuit. Figure 1A As shown, R1 and R2 form a sensor element (e.g., a half-Wheatstone bridge), and resistors R3 and R4 have fixed resistances. For example, a change in pressure corresponds to a change in R1 and / or R2. For example, an increase in pressure may correspond to an increase in R1 and a decrease in R2. Specifically, pressure is proportional to the voltage across the bridge V BC If R1 equals R2 and R3 equals R4, then the voltage V BC will be 0V, and the current through R1 and R3 will be the same as the current through R2 and R4. However, if R1 and / or R2 change (e.g., due to a change in pressure), the voltage V BC will increase or decrease accordingly and can be measured by the voltage measurement circuit. Then the BC Measure the change in pressure.

[0050] In some variations, conventional Wheatstone bridge sensors separate R3 and R4 from sensor elements R1 and R2. In addition, R3 and R4 can be set as close as possible in resistance. For example, as long as R3 is equal to R4 so that V BC will depend on the ratio of R1 and R2, R1 does not need to be equal to R3. However, when R3 is not equal to R4, V BCAn error (e.g., an offset) may be included. This offset may be measured and used to calibrate the sensor (e.g., when manufacturing or turning on the sensor). For example, V may be measured at a first predetermined pressure and a second predetermined pressure. BC Linear regression can be used to determine the inherent offset and gain of the sensor circuit so that the sensor can be calibrated.

[0051] Similarly, R1 and R2 need not have any inherent relationship under any one condition. For example, at ambient pressure R1 may be 2000.5 ohms and R2 may be 2002.1 ohms, and when R3 is equal to R4 V BC It may not be 0 V. However, the inherent offset in the pressure measurement can be removed by simply taking another measurement at a different pressure.

[0052] Figure 1B is a schematic diagram of another Wheatstone bridge sensor 150 in which the sensor elements R1 and R2 are further away from the rest of the circuit. For example, when used in a blood flow control device such as an intravascular balloon catheter, R1 and R2 may be inside the body and about 50 cm to about 100 cm away from the rest of the circuit (e.g., V, R3, and R4). For example, the Wheatstone bridge circuit configured as a pressure sensor preferably has a size that is smaller than the diameter of the body cavity (e.g., artery, vein) in which it is placed. In some variations, the pressure sensor may include R1 and / or R2 and a set of wires (e.g., three wires - a wire from V to R1 and R2, a wire from R1 to R3, and a wire from R2 to R4) for connecting to the remaining elements of the circuit disposed outside the patient's body. In addition, in the event of damage to the sensor and / or wire, the voltage and / or current applied to the pressure sensor may be relatively low to reduce heat and patient risk. For example, the resistors R1 to R4 may be about 2K ohms, and the voltage applied to the pressure sensor may be between about 2V and about 5V, so that the current is less than about 1 mA. For these values, the differential voltage V BC It can be changed between about 10 μV per mmHg pressure change and about 20 μV per mmHg pressure change. A voltage measurement circuit with a resolution of less than about 5 μV can be configured to provide a pressure measurement resolution of about 0.25 mmHg. However, an amplifier configured to amplify about 200 times or more is generally required.

[0053] However, when used in such a configuration, for example, in a blood flow control device, the length of the wires may reduce sensor accuracy. For example, the wires may act as antennas that pick up both common mode noise and differential noise. Conventionally, removal of this common mode noise requires a common mode low pass filter, and even with the filter a differential amplifier with a high common mode rejection ratio may still be required. In addition, the wires are typically not matched, so that a differential low pass filter is typically used to filter the differential signal before input to the differential amplifier. Even so, the low pass filter itself may add very low frequency offsets, phase delays, and attenuation at higher heart rates to the signal, all of which must be compensated for in software.

[0054] Conventional sensors are subject to different offsets that may reduce the accuracy of the measurement. In some variations, a conventional sensor may include an offset compensation circuit that includes one or more of a differential amplifier, a potentiometer, and a DAC configured to compensate for the inherent offset introduced by R1 and R2. However, even the offset compensation circuit may add a small gain error to the measurement. In addition, silicon-based sensors may be sensitive to temperature changes. For example, a temperature change of 1°C may correspond to an offset change of greater than 1 mmHg. In some variations, the offset compensation circuit may include a circuit configured to measure a separate voltage V B and V C The design and implementation of the offset compensation circuit may result in additional cost, size, weight, and manufacturing complexity.

[0055] Figure 2A is a schematic block diagram of a sensor used in a medical device that includes some electronics inside the body and some electronics outside the body. A piezoresistive MEMS sensor can be conceptualized as a combination of R1 and R3 (from Figure 1B and FIG. 1C ), where R2 and R4 are implemented in a circuit mounted on a small printed circuit board (PCB).

[0056] Although Figure 2AThe solid state pressure transducer (SSPT) circuit system shown is known, but there are some limitations. For example, one limitation is related to balancing the bridge. In addition to R2 and R4, the small PCB also includes several potentiometers (variable resistors) that must be adjusted to bring the default value of VOut within a certain range so that it is within the capabilities of the amplifier and analog-to-digital converter (ADC). For example, if the value of VOut is too high at 0 mmHg pressure, the output of the amplifier may be greater than the output that the ADC can measure at higher pressures (such as 200 mmHg). If the system is to measure negative pressures and the amplifier and ADC are simplified to avoid measuring negative voltages, the value of VOut will be greater than 0 at the lowest pressure. At the time of manufacturing, the potentiometer can be adjusted so that VOut is relatively small at 0 mmHg. Even with these potentiometer adjustments, additional offset adjustments using active circuits (such as in chips like PGA309) can also be used to compensate for variations due to different atmospheric pressures, handling negative pressures, and other variations that occur at other stages in the manufacturing process. These characteristics can affect the manufacturing and testing costs of the SSPT.

[0057] Another limitation is due to power supply and ground noise. The Wheatstone bridge arrangement is susceptible to current being fed into R1 and R3 (e.g. Figure 1B 1C ). Any noise on this line can result in corresponding variations in VOut. Similarly, if the electrical ground is shifted, asymmetries in stray capacitance and resistance can result in significant variations in VOut. Further down the path, the amplifier and ADC may not have the same response to shifts in the supply voltage or ground, and therefore these voltage variations may manifest themselves as noise in the measurements.

[0058] Another limitation is due to electrical noise on the long wires in the catheter. The wires can act as unintended antennas, and a 50 cm to 100 cm wire in a catheter may have an undesired amount of gain over a wide frequency range. The energy captured by the wire (also known as the antenna effect) changes the expected value, and this change is called "noise". The noise can be dynamic and can have frequencies from a few Hertz (Hz) to hundreds of millions of Hertz. This type of noise is often referred to as radio frequency (RF) noise. Specifically, the 60 Hz alternating current (AC) power currently used in the United States and the 50 Hz AC currently used in Europe can result in particularly high noise levels.

[0059] like Figure 1BAs shown, the excitation voltage (V-Exc) is directly coupled to the resistors R1 and R2 of the Wheatstone bridge. If electrical noise (e.g., variation) is picked up on the V-EXC wire, this will have the same effect as power supply noise. If the noise is picked up on only the SIG+ or SIG- wires, this will also directly change VOut. If the same noise is picked up on both the SIG+ and SIG- wires, this creates "common mode" noise. An ideal differential amplifier will ignore this noise because it theoretically does not change the difference between the voltages on SIG+ and SIG-. However, in practice, the various resistances and capacitances along the two paths are not the same, and this common mode noise entering the amplifier causes the difference.

[0060] Because of noise limitations, a set of filters are usually used. A first differential filter is usually used before VOut is presented to the amplifier. This filters out high frequency common mode noise as well as some differential noise. Another low pass filter is then placed after the amplifier. This cuts out high frequency noise that would cause the ADC to "alias" the noise to lower frequencies. Finally, a digital low pass filter is sometimes used in software to remove any noise captured by the ADC.

[0061] Some electrical noise may be difficult to filter out, such as that found in common emergency scenarios - electrosurgical pencil use and cardiac defibrillation. Regulatory agencies have recognized this limitation, and specifications such as 60601-1 and 60601-2-34 take into account the recovery time after the loud noise stops.

[0062] Another limitation of SSPT is related to run-time calibration. When using SSPT, there may be variations in the voltages supplied to the sensors, amplifiers, and ADC chips. These variations may be due to changes in the temperature of those circuits. They may also be due to variations in the output of various power supplies, especially those powered by batteries. Sensors may also have variations with respect to temperature. This typically requires additional circuitry and manufacturing costs to compensate for variations due to temperature.

[0063] Another limitation of SSPT is related to interoperability. For a REBOA catheter with SSPT sensors above and below the balloon and a display unit outside the body, it may sometimes be desirable that the catheter itself could be interchangeable so that only one display unit is needed to service multiple catheters. Because calibration must be performed on the entire analog circuit (sensor in the catheter plus electronics in the display unit), the "boundary" of interchangeability would need to be at the ADC. This may require separate infrastructure for the analog and digital circuits and would add even more cost.

[0064] Figure 2Bis a schematic block diagram of a conventional analog path for a sensor 200, such as a Millar sensor, which may have a relatively small differential voltage variation per mmHg. For example, the sensor 200 may have a μV / V / mmHg variation, where a 2.74V excitation of a Wheatstone bridge may correspond to 13.7 μV / mmHg. In order to achieve a resolution sufficient to allow the use of a 3.3V ADC, an amplification of greater than 200 times may be required. The offset compensation circuit may include a PGA309 chip that is configured to compensate for the offset and adjust the gain so that the output is within a predetermined range of the ADC. The systems, devices, and methods described herein address the shortcomings of conventional techniques.

[0065] I. Sensor Systems and Equipment

[0066] A. Advantages over existing technologies

[0067] The sensors described herein may provide a number of advantages over conventional sensors using, for example, a known Wheatstone bridge. Examples of these advantages include, but are not limited to, the following.

[0068] First, the sensors described herein (e.g., pressure, force) can utilize MEMS circuit arrangements, where analog-to-digital conversion can be performed directly on the sensor die. In some variations, the sensors described herein do not have a very small differential voltage as an output, but can generate a digital output (e.g., a serial digital stream), such as a standard universal asynchronous receiver transmitter (UART), which can be easily read directly by a computing device such as an off-the-shelf microcontroller. Second, the use of the sensors described herein can reduce manufacturing costs, system size, and system power, and can allow for increased flexibility in how to prototype, design, and manufacture devices (e.g., medical devices) that utilize these sensors. Space and power consumption may be important considerations for some equipment pieces carried into harsh environments. The development of fully digital pressure sensors (such as those described herein) greatly simplifies the back-end electronics of these devices. For example, at least because the sensors described herein can use power and precise clocks as inputs in some variations, the computing device can be greatly simplified compared to known technologies: there are only power sources, clock sources, and circuits for receiving serial messages (e.g., UART) and converting them into wired or wireless formats. Thus, in some variations, the displays may be spaced any arbitrary distance apart. Additionally, because the sensor is inherently always in an "output mode" (rather than a read-response mode), the output value may be transmitted to more than one computing device.

[0069] Third, as will be discussed in greater detail herein, the described sensors can provide a digital output (e.g., a sequential digital stream indicative of pressure) that can allow portions of a device (e.g., in the case of a medical device comprising an elongated body such as a catheter, a catheter shaft) to be disconnected from external electronics, allowing the electronics to be used with multiple devices. In addition, the sensors described herein also allow portions of the electronics to be replaced in the event that the electronics become damaged and / or run out of power. In variations in which the sensors described herein are utilized in a medical device (e.g., a blood flow regulation device), the portion of the medical device that is advanced into the patient's body can remain within the patient's body while the external electronics (e.g., a computing device) are replaced.

[0070] Fourth, the sensor described herein can provide a higher quality digital output than a conventional Wheatstone bridge sensor that provides an analog signal. For example, particularly for use in pressure sensing applications, the digital output can have, for example, a noise tolerance that is at least 10,000 times greater than the analog signal. As an example, if the digital output is nominally 3.3V for logic 1 and nominally 0V for logic 0, the receiver can tolerate, for example, a noise level of 1V and still be able to distinguish between 1 or 0. For an analog-based Wheatstone bridge, a noise level of only 100 microvolts may correspond to a change of up to 4mmHg in the pressure reading. This may be too much error for high-fidelity physiological monitoring that can form the basis of medical devices. In addition, the digital messaging scheme also increases signal fidelity by allowing the addition of an error detection bit, which can further increase the confidence that the received message has not been corrupted. Additionally, in some variants, such as those in which the computing device receives a digital value, the temperature of the computing device may have little effect, and the circuit that generates the digital value may not need to be compensated or calibrated. Additionally, having a digital output from the sensor can eliminate the amplification stage previously used with analog solid-state pressure sensors or used with fluid column based pressure sensors. Since there is no analog amplifier, there is also no need to match the voltage between the amplifier and the associated ADC.

[0071] Fifth, in some variations, the sensors described herein utilize sensor wires that are immune to or less susceptible to RF-induced noise. For example, the sensors described herein may utilize sensor wires that are smaller than conventional sensor wires (e.g., <0.1 mm), and thus the sensor wires may be too small to be susceptible to RF-induced noise.

[0072] Additionally, having only the digital signal traverse long wires eliminates the need for almost all low-pass filters. This saves space on the sensor circuitry, reduces complexity, etc.

[0073] Sixth, compared to known technologies, the sensors described herein are readily adaptable across a variety of silicon processes, thus allowing them to be versatile across processes.

[0074] Seventh, the sensors described herein can provide improved fault detection compared to conventional sensing techniques. For example, if any sensor wire is damaged, the computing device (e.g., a microcontroller) can detect the fault within a short time frame (e.g., 1 sampling period) because the digital output from the sensor will stop.

[0075] Eighth, the sensors described herein easily allow the use of various run-time diagnostics by changing the input clock rate or changing the supply voltage, which is not possible in many conventional sensing technologies.

[0076] While there are many advantages to utilizing the sensors described herein, there are also challenges in creating sensors with built-in analog-to-digital converters (ADCs). For example, it may be desirable for the ADC to add minimal size to the silicon die so that the ADC still fits within the size constraints of the device for a particular application, such as, for example, within an elongated body in a medical device. For example, it may also be desirable for the sensing element and ADC to tolerate voltage variations because, in some implementations, the sensor die may be at least 50 cm to 100 cm from a power source. For example, it may also be desirable for the ADC to be able to tolerate variations in sensor location (such as, for example, within a patient's body) or temperature.

[0077] Some known analog-to-digital conversions are performed using sigma-delta or successive approximation techniques. This may require complex circuits that must be adapted to each silicon process and may be sensitive to operating voltage and temperature. Fig.11A and Fig. 11B As shown and discussed, some variations use methods for generating digital outputs from essentially analog sensor measurements. For example, some variations use a set of oscillating rings, a set of counters and latches, and some mathematical calculations to perform analog-to-digital conversion, as will be discussed in more detail herein.

[0078] B. Sensor System

[0079] In general, a sensor system may include one or more of the components necessary to measure and optionally output a parameter using a system as described herein. Figure 3A block diagram of an exemplary solid-state sensor system 300 is depicted in FIG. System 300 may include one or more of a sensor 302, a controller 320 (e.g., a device controller, a microcontroller), and a computing device 340. In some variations, sensor 302 may be coupled to one or more of controller 320 and computing device 340 via a network (e.g., via a wired or wireless connection). Sensor 302 may be configured to measure one or more parameters (e.g., temperature, voltage, force, pressure, light amplitude, audio amplitude, radiation). The measured parameter may correspond to any parameter capable of changing the time delay of a delay element. For example, one or more of resistance, capacitance, and inductance may change in response to a change in the parameter. In some variations, the measured parameter may be based on another circuit (e.g., a resonator) coupled to an oscillator ring so that the measured parameter is based on a second-order method. In some variations, system 300 may be configured to output the sensor measurement via controller 320. For example, the controller 320 may be configured to output a digital signal (e.g., of a measured parameter) to the computing device 340 without analog-to-digital conversion. In this way, the system 300 may be formed without an ADC, which may reduce one or more of the size, cost, and manufacturing complexity of the system 300.

[0080] Return to reference Figure 3 In some variations, the sensor system 300 may include one or more of a sensor 302 and a controller 320. The sensor 302 may include one or more of a first circuit 304, a second circuit 306, an optional third circuit 308, an optional fourth circuit 310, an optional rate counter 312, an optional delay calculator 314, an optional latch 316, an optional divider 317, and an output device 318. In some variations, one or more of the first circuit 304, the second circuit 306, the third circuit 308, and the optional fourth circuit 310 may include a ring oscillator circuit as described in more detail herein. In some variations, the divider 317 may include one or more sets of circuit systems configured to divide an input signal (e.g., convert a 32,768,000 Hz clock to a 16,384,000 Hz clock). In some variations, the counter 312 may include one or more sets of circuitry configured to count the number of oscillations (i.e., ticks) at the first circuit 304, the second circuit 306, the third circuit 308, and / or the fourth circuit 310 during a sampling period. In some variations, the latch 316 may include one or more sets of circuitry configured to store a representation of the count captured by the counter 312. In some variations, the output device 318 may be configured to send a signal indicative of the count captured by the counter 312 and / or stored in the latch 316. In some variations, the output device 318 may include a shift register, an output register, a serializer, etc.

[0081] Controller 320 may include one or more of processor 322, memory 324, input device 326, output device 328, and communication device 330, each of which is described in greater detail herein. In some variations, system 300 may be disposed on a single substrate (e.g., a single die) or on multiple substrates. For example, sensor 302 may be disposed on a first substrate and controller 320 may be disposed on a second substrate.

[0082] In some variations, input device 326 may be configured to receive a signal based on a set of output clock signals from sensor 302. In some variations, output device 326 may be configured to output data associated with system 300 as a digital signal. In some variations, processor 322 and memory 324 may be configured to control sensor system 300. In some variations, communication device 330 may be configured to communicate with one or more components of system 300 and computing device 340 (e.g., mobile phone, tablet, laptop, desktop PC). In some variations, computing device 340 is a microcontroller.

[0083] Note that although Figure 3 The computing device 340 is shown as being separate from the controller 320 , but in some variations the controller 320 and the computing device 340 may be a single unit (eg, a single chip).

[0084] In some variations, multiple sensors may be coupled to each other. For example, in some variations, multiple sensors (two sensors, three sensors, four sensors, or more sensors) may be coupled to each other in series (i.e., daisy-chained). In these variations, the clock rate may be modified to account for the daisy-chained sensors. As an example, if a 32,768 Hz input clock may have been used to measure values ​​from a single sensor, the clock rate in the daisy-chained variation may be 32,768 Hz multiplied by the number of sensors in the daisy chain (e.g., if two sensors are daisy-chained, a 65,536 Hz clock is used, if three sensors are daisy-chained, a 98,304 Hz clock is used, and so on). Additionally, an input may be added to a serializer (i.e., a shift register) that receives bits from an upstream sensor, such as Fig. 14B As shown. Thus, a digital output (e.g., a UART-type serial output) can report the values ​​of multiple latches from multiple sensor chips to a computing device. In some variations, multiple sensors can be read using only 4 wires to / from the computing device: a power wire, a ground wire, and a clock wire can each be coupled to all sensors, and the output of each sensor can be coupled to the "shift-in" of the subsequent sensor until the final sensor in the chain produces a digital output that can be coupled to, for example, a UART input of the computing device.

[0085] An example of daisy chaining sensors is shown in Fig.14A . A first sensor 1402 may measure a first value, which may be provided to a second sensor 1404 (e.g., as an input to its serializer), which may measure a second value, which may be provided to a third sensor 1406 (e.g., as an input to its serializer), which may measure a third value, and may generate a digital output ("SER OUT") that is a serial list of each of the values ​​measured by each of the sensors 1402, 1404, and 1406. In some variations, each value measured by each sensor is cascaded to the input of the serializer provided to that sensor (if an input is provided for that sensor). For example, "SER OUT" may be a list of bits indicating a bit representing a value measured by sensor 1402, followed by a bit representing a value measured by sensor 1404, followed by a bit representing a value measured by sensor 1406. In some variations, each value measured by each sensor is separated from other values ​​measured by other sensors using a known indicator (such as a predetermined combination of bits known to the processor). The "SER OUT" may be provided to a computing device that is configured to then use the "SER OUT" to identify each value measured by each sensor. Sensors 1402, 1404, and 1406 may all measure the same parameter (e.g., pressure), all measure different parameters (e.g., pressure, force, light amplitude), or a combination of some sensors measuring the same parameter and some sensors measuring different parameters. Fig.14A As shown, the daisy chain of sensors may have only 4 wires - voltage (VCC), clock (CLK), serial output (SER OUT), and ground (GND). In one example, the sensors may be placed inside a person's body, and the 4 wires may be connected to a computing device (e.g., a microcontroller) that is further away from the sensors (e.g., 50 cm to 100 cm away) and is configured to determine each value measured by sensors 1402, 1404, and 1406. Using something like Fig.14A A variation of may allow a single UART to read multiple sensors and may also greatly reduce the overall number of wires routed within a system with many sensors (eg, because there is only one SER OUT for multiple sensors rather than each sensor having its own SER OUT).

[0086] Fig.15A top view, a side view, a front view, and a perspective view of an exemplary chip are shown. Chip 1500 may include a sensor. As shown, chip 1500 may include a plurality of wire bonding pads 1502 positioned above a complementary metal oxide semiconductor (CMOS) bare die 1506. More specifically, chip 1500 may include four bonding pads, one bonding pad each for voltage, clock, serial output, and ground, and wire bonding pads 1502 may be positioned on the top surface of CMOS bare die 1510. Chip 1500 may also include a sensor delay-microelectromechanical system (MEMS) piezoresistive sensor die 1508. MEMS piezoresistive sensor die 1508 may be configured to delay the number of oscillations through one or more ring circuits based on a parameter to be measured (e.g., pressure). Chip 1500 may also include a CMOS circuit system 1504, which may include the remaining sensor components (e.g., oscillator ring, latch, counter, serializer). In some variations, as will be discussed herein, chip 1500 may be placed in a sensor housing. In some variations, the CMOS bare die 1506 may have a width of about 200 microns to about 500 microns, a width of about 250 microns to about 450 microns, a width of about 300 microns to about 400 microns, a width of about 330 microns, a width of less than 200 microns, and / or a width of greater than 500 microns (including all values ​​and subranges therein). In some variations, each wire bonding pad from the wire bonding pads 1502 may have a width of about 20 microns to about 100 microns or about 30 microns to about 90 microns (including all values ​​and subranges therein), and / or a length of about 150 microns to about 250 microns or about 175 microns to about 225 microns (including all values ​​and subranges therein). In other variations, each wire bonding pad from the wire bonding pads 1502 may have a width of less than 20 microns, a width of greater than 100 microns, a length of less than 150 microns, and / or a length of greater than 225 microns. In further variations, CMOS circuitry 1504 may have a width of about 200 microns to about 300 microns or about 225 microns to about 275 microns, including all values ​​and subranges therein, and / or a length of about 50 microns to about 150 microns or about 75 microns to about 125 microns, including all values ​​and subranges therein. Alternatively, CMOS circuitry 1504 may have a width of less than 200 microns, a width of greater than 300 microns, a length of less than 50 microns, and / or a length of greater than 125 microns.In still other variations, the MEMS piezoresistive sensor 1508 may have a width of about 200 microns to about 300 microns or about 225 microns to about 275 microns, including all values ​​and subranges therein, a length of about 500 microns to about 700 microns or about 550 microns to about 650 microns, including all values ​​and subranges therein, and / or a height of about 200 microns to about 300 microns or about 225 microns to about 275 microns, including all values ​​and subranges therein. In some variations, the MEMS piezoresistive sensor 1508 has a width of less than 200 microns, a width of greater than 300 microns, a length of less than 500 microns, a length of greater than 700 microns, a height of less than 200 microns, and / or a height of greater than 300 microns.

[0087] In some implementations, the sensor (eg, included in chip 1500) may be incorporated into an application specific integrated circuit (ASIC). Fig.16 A block diagram of an exemplary sensor 1600 incorporated in an ASIC is shown. As shown, the sensor 1600 may include a plurality of wire bonding pads 1606 (eg, 4 wire bonding pads), similar to Fig.15 1502 as depicted in the sensor of FIG. The four wire bonding pads may be operably coupled to a digital logic device 1604 configured to oscillate the plurality of rings and count the number of oscillations of each of the rings. The sensor 1600 may also include a MEMS piezoresistive sensor 1602 that may be configured to delay the number of oscillations at the first oscillation ring (rather than at the second oscillation ring) via resistance based on a parameter value to be measured.

[0088] a. Oscillator circuit

[0089] In general, the oscillator circuits (e.g., compensated ring oscillators) described herein may be configured to receive an input clock signal and generate an output clock signal having a frequency greater than the input clock signal. The oscillator circuit may include one or more (e.g., multiple) delay circuits (e.g., inverter circuits, such as Schmitt trigger inverters) arranged in a ring configuration. The oscillator circuit may be configured to generate an output clock signal having a predetermined ratio (e.g., the output clock signal is an integer multiple of the input clock signal) by compensating for inherent circuit offsets such as temperature and voltage by adjusting the delay of the oscillator circuit. Circuits suitable for use in the systems, devices, and methods herein are described in U.S. Patent No. 6,911,872, filed on March 25, 2003, issued on June 28, 2005, and entitled "Circuit and Method for Generating a Clock Signal," which patent application is hereby incorporated by reference in its entirety.

[0090] Figure 4 4 is a schematic diagram of an illustrative variation of an oscillator circuit 400, which includes a plurality of delay circuits 410 and an adjustable delay circuit 420, a rate counter circuit 430, and a delay calculator circuit 440 arranged in a ring configuration. The circuit 400 is configured to receive an input clock signal and use the adjustable delay circuit 420 calculated by the delay calculator circuit 440 to generate an output clock signal having a predetermined ratio between the input clock signal and the output clock signal. The adjustable delay circuit 420 can be configured to set a predetermined delay based on the calculated adjustable delay. That is, the adjustable delay can be calculated by comparing the ratio of the output clock signal (e.g., the ringing frequency) to the input clock signal and adjusting the adjustable delay according to the predetermined ratio. In some variations, the adjustable delay circuit 420 includes one or more of a resistor-capacitor delay circuit, a resistor-inductor delay circuit, and a capacitive delay circuit.

[0091] Rate counter circuit 430 may be configured to count the number of output clocks that occur for each single count of the input clock.Delay calculator circuit 440 may be configured to calculate the difference between the output of rate counter circuit 430 and a predetermined ratio.

[0092] The frequency of the output clock signal may be greater than the frequency of the input clock signal. In some variations, the plurality of delay circuits 410 may be coupled to a multiplexer (not shown). In some variations, the first plurality of inverter circuits may have a closed-loop configuration with positive feedback. In some variations, the oscillator circuit 400 may be disposed on one or more substrates (e.g., a silicon die).

[0093] An exemplary operation of the oscillator circuit 400 is described below. For a predetermined ratio of 1000 and a rate counter value of 998 output clock counts for each input clock count, the delay calculator circuit 440 can calculate an adjustable delay that slows down 2 counts per input clock run, and use the adjustable delay circuit 420 to set the adjustable delay. As another example, an input clock signal with a frequency of 32,768 Hz and a predetermined ratio of 1000 corresponds to an output clock signal with a frequency of 32,768,000 Hz. Therefore, the total delay of the loop can be about 30.52 ns (1 / 32,768,000). If the propagation time of a single delay circuit (e.g., an inverter circuit) is about 50 picoseconds, the oscillator circuit can include about 61 delay circuits. It should be understood that input clock signals with a frequency of, for example, 32.768 kHz can have high accuracy because they are based on large quartz crystals cut to precise sizes. For example, crystals used in digital watches and computer systems typically achieve accuracies within the range of + / -10 ppm (+ / -0.001%) or better. In addition, these input clock signals can be transmitted over relatively long distances while maintaining immunity to noise. In some variations, the input clock signal may have a frequency of 32,768 Hz, or integer fractions of this rate (e.g., 16,384 Hz, 8,192 Hz, etc.).

[0094] For silicon-based implementations, the oscillator circuit 400 compensates for variations in temperature, voltage, and the inherent speed of the silicon substrate. For example, an increase in temperature corresponds to an increase in the propagation time through the delay element and a slower output clock signal. Conversely, an increase in voltage corresponds to a shorter propagation delay and a faster output clock signal. In some variations, the adjustable delay circuit 420 may include a range sufficient to compensate for variations in propagation delays within a single silicon process. For example, a substrate (e.g., silicon die) from one manufacturing batch may have a propagation delay that varies by up to about 20% from another substrate from another manufacturing batch, even if both substrates are subjected to the same voltage and temperature. The differences in silicon from manufacturing batch to manufacturing batch are sometimes referred to as "silicon skew."

[0095] Figure 5 5 is a schematic diagram of an exemplary variation of a sensor including a plurality of oscillator ring circuits. For example, sensor 500 may include a first circuit 510, a second circuit 520, a third circuit 530, and a delay calculator circuit 540. Each of the first circuit 510 and the second circuit 520 may include a circuit related to Figure 4A plurality of delay circuits and rate counter circuits similar to those shown and described are arranged in a ring configuration. In addition, the first circuit 510 may include a first adjustable delay circuit 512, and the second circuit 520 may include a second adjustable delay circuit 522. The first circuit 510 and the second circuit 520 may be configured to receive an input clock signal and use the corresponding adjustable delay circuits 512, 522 calculated by the delay calculator circuit 540 to generate a corresponding output clock signal, the corresponding output clock signal having a predetermined ratio between the input clock signal and the output clock signal. The adjustable delay circuits 512, 522 may be configured to set a predetermined delay based on the calculated adjustable delay. That is, the adjustable delay may be calculated by comparing the ratio of the output clock signal of the first circuit 510 to the input clock signal and adjusting the adjustable delays of both the first circuit 510 and the second circuit 520 according to the predetermined ratio. The delay calculator circuit 540 may be configured to calculate the difference between the output of the rate counter circuit of the first circuit 510 and the predetermined ratio. The frequencies of the first output clock signal 510 and the second output clock signal 526 are each greater than the frequency of the input clock signal.

[0096] In some variations, the first circuit 510 may include a first oscillator circuit (similar to the oscillator circuit 400). Similarly, the second circuit 520 may include a second oscillator circuit. The first circuit 510 may be configured to receive an input clock signal and output a first output clock signal 514 using an adjustable delay, the first output clock signal having a predetermined ratio between the input clock signal and the first output clock signal 514. In some variations, the second circuit 520 may be configured to receive an input clock signal and output a second output clock signal 526 using an adjustable delay. In some variations, a third circuit 530 may be coupled to the first circuit 510 and the second circuit 520, and the third circuit 530 may be configured to generate a third signal 532 based on a difference between the first output clock signal 514 and the second output clock signal 526. The third signal 532 may correspond to a measured parameter. For example, the third signal 532 may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude. In some variations, the third signal 532 may be processed to output a parameter signal corresponding to a unit of measurement (eg, mmHg).

[0097] In some variations, the first circuit 510 includes a first plurality of delay circuits arranged in a ring configuration. The first plurality of delay circuits may include a first plurality of inverter circuits and a first adjustable delay circuit 512. The first adjustable delay circuit 512 may include a first rate counter. The first plurality of inverter circuits may be coupled to a first multiplexer. The first plurality of inverter circuits may have a closed-loop configuration with positive feedback. The first delay circuit may include a first resistor-capacitor delay circuit.

[0098] The first output clock signal 514 may vary based on a first set of parameters, and the second output clock signal 526 may vary based on a second set of parameters that are different from the first set of parameters. For example, the first set of parameters may include one or more of temperature and voltage. In some variations, the second set of parameters includes temperature, voltage, and one or more of: force, pressure, light amplitude, audio amplitude, and resistance or capacitance corresponding to a chemical or physical reaction. That is, the second set of parameters may include the first set of parameters and at least one additional parameter.

[0099] In some variations, the third signal 532 may be processed to calculate a difference relative to a starting condition (eg, tare) in the second output clock signal 516. For example, the tare signal may be provided as a separate input or as a signal using in-band encoding of the input clock signal.

[0100] In some variations, the second circuit 520 includes a second plurality of delay circuits arranged in a ring configuration. The second plurality of delay circuits may include a second plurality of inverter circuits and a second adjustable delay circuit 522. The second adjustable delay circuit 522 may include a second rate counter. The second plurality of inverter circuits may be coupled to a second multiplexer. The second plurality of inverter circuits may have a closed-loop configuration with positive feedback. The second adjustable delay circuit 522 may include one or more of a resistor-capacitor delay circuit, a resistor-inductor delay circuit, and a capacitive delay circuit. The second circuit 520 may include at least one delay circuit configured to change based on at least one additional parameter different from the first circuit 510.

[0101] In some variations, the second plurality of delay circuits may include delay circuits identical to the first group of delay circuits and at least one additional delay circuit configured to change based on a parameter to be measured (e.g., pressure). In this way, the output clock signals 514, 526 from the respective first circuit 510 and second circuit 520 may differ as the parameter to be measured (e.g., pressure) changes. In variations in which the first circuit 510 and the second circuit 520 are disposed on the same substrate (e.g., the same silicon die), the adjustable delays due to temperature and voltage offsets will be the same for the first circuit 510 and the second circuit 520. Therefore, the difference between the first output clock signal 514 and the second output clock signal 526 will be attributed to changes in the measured parameter (e.g., pressure) and will be independent of offsets such as temperature, voltage, and silicon skew. In some variations, the additional delay circuits of the second circuit 520 may include one or more of a resistor-capacitor delay circuit, a resistor-inductor delay circuit, and a capacitive delay circuit. Any physical property (e.g., pressure, force, light amplitude, audio amplitude, voltage) that can result in a change in electrical propagation time (e.g., delay) can be measured in this manner. For example, sensor 500 can be used for electrochemical analysis where a chemical reaction results in a change in resistance or capacitance. The described systems, devices, and methods reduce circuit complexity and size by avoiding precision current sources and voltage measurement ADCs.

[0102] In some variations, the sensor 500 may be disposed on one or more substrates (e.g., a silicon die). For example, a single substrate may include the first circuit, the second circuit, and the third circuit. In other variations, the first substrate may include one of the first circuit and the second circuit, and the second substrate may include the other of the first circuit and the second circuit. In addition, each circuit of the sensor 500 may be disposed on its own substrate or on any combination of substrates.

[0103] An exemplary operation of the oscillator circuit 500 is described below. For an input clock signal having a frequency of 32,768 Hz and a first output clock signal having a frequency of 32,768,000 Hz, at a predetermined sampling rate of 200 Hz (e.g., a 5 millisecond sampling period), a span of 1000 mmHg pressure (minimum to maximum), and a predetermined resolution of 0.25 mmHg, 4,000 quantization levels are required (1,000 mmHg / 0.25 mmHG=4,000 quantization levels). In this case, the second circuit 520 may have approximately 163,840 clocks per 5 ms sampling period. One clock period is 1 / 32,768,000 seconds (30.52 ns). Therefore, for every 0.25 mmHg of pressure, the delay changes by 30.52 ns. It should be understood that 4,000 quantization levels are much less than 163,840 clocks per 5 millisecond period, so that a digital counter can be used to measure the count. If the sensor measurement requires more than 30.52ns for every 0.25mmHg of pressure, a faster clock rate can be used. Conversely, if the variation in delay is greater than 30.52ns for every 0.25mmHg of pressure, a slower clock can be used.

[0104] In some variations, an optional fourth circuit (e.g., Figure 3 The fourth circuit 310 in the embodiment of the present invention may be configured to measure a parameter different from that of the second circuit 520. For example, the fourth circuit may include a delay circuit configured to change based on temperature. The fourth circuit may have a configuration similar to the second circuit 520 described herein.

[0105] In some variations, the fourth circuit may be coupled to the third circuit. The fourth circuit may be configured to receive an input clock signal and output a fourth output clock signal using an adjustable delay. The third circuit may be configured to generate a fifth signal based on a difference between the first output clock signal and the fourth output clock signal. The fifth signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude. In this way, the sensor 500 can be configured to measure multiple parameters while compensating for offset without an offset compensation circuit.

[0106] In some variations, the sensor 500 may be powered by a set of three wires: a first wire associated with a positive voltage, a second wire associated with ground, and a third wire associated with an input clock signal (which may be referenced to ground). In some variations, power may be derived only from the input clock signal.

[0107] In some variations, the sensors described herein may be configured to include about 5,000 gates and about 10,000 gates / mm. 2 In some embodiments, the die may include a substrate greater than about 0.3 mm.2 In some variations, the sensor 500 may include a low pass filter to reduce noise on the power supplied to the delay element (eg, noise above 16.384 kHz corresponding to the Nyquist rate of a 32.768 kHz crystal).

[0108] Fig. 9A and Fig. 9B A schematic diagram of two different ring oscillator circuits that can be used in combination to provide corresponding count values, where the count values ​​from the two different ring oscillator circuits can be used to determine the value of a parameter of interest (e.g., pressure, force, light amplitude, audio amplitude, radiation, resistance or capacitance corresponding to a chemical or physical reaction, etc.). Fig. 9A A schematic diagram of an oscillator circuit 900A is shown, which includes a set of delay circuits 910A and a parameter-based delay circuit 920 (i.e., a first ring circuit), a rate counter circuit 930A (i.e., a counter), and a latch circuit 950A (i.e., a latch) arranged in a ring configuration. The delay of the parameter-based delay circuit 920 changes based on the parameter of interest (e.g., the delay increases with decreasing pressure, the delay decreases with increasing pressure, etc.). Fig. 9B A schematic diagram of an oscillator circuit 900B is shown, which includes a set of delay circuits 910A (i.e., a second ring circuit), a rate counter circuit 930B, and a latch circuit 950B arranged in a ring configuration. The oscillation rate of the second ring circuit will change based on a first set of parameters (e.g., temperature and voltage) that do not include the parameter of interest, while the oscillation rate of the first ring circuit will change based on the first set of parameters and the parameter of interest. Oscillator circuit 900A may function similarly to a measurement circuit for determining a tentative predicted value of the parameter of interest, and oscillator circuit 900B may function similarly to a calibration circuit for adjusting the tentative predicted value by compensating for variations potentially caused by the first set of parameters.

[0109] refer to Fig. 9A, the oscillation rate of the first ring circuit may be sampled at a first sampling rate (i.e., a predetermined sampling rate), and the rate counter circuit 930A and the latch circuit 950A may be used to count and store the number of oscillations of the first ring circuit during each sampling period (e.g., at each rising edge of the sampling rate clock), respectively. For example, if the first ring circuit oscillates at 100 MHz and the sampling rate is 256 Hz (approximately 1 sample every 4 ms), the rate counter circuit 930A will count approximately 400,000 oscillations of the first ring circuit every 4 ms. For each sampling period, the latch circuit 950A may receive the output count signal and store a representation of the count value counted by the rate counter circuit 930A in that sampling period for future processing (as indicated in the output count signal). As previously mentioned, the number of oscillations at the first ring circuit may vary across sampling periods based on the first set of parameters and at least one additional parameter (i.e., a parameter of interest). Therefore, the output of the latch circuit 950A may be a nearly continuous representation of the behavior of the first ring circuit with respect to the first set of parameters and the parameter of interest. In some variations, the delay circuit 910A may include a set of inverters; in some variations, the set of inverters may be coupled to a multiplexer. In some variations, the set of inverters is in a closed loop configuration with positive feedback. In some variations, the first loop circuit may include one or more of a resistor-capacitor delay circuit, a resistor-inductor delay circuit, and a capacitive delay circuit.

[0110] refer to Fig. 9B, the oscillation rate of the second ring circuit can be sampled at a second sampling rate (i.e., a predetermined sampling rate), and the rate counter circuit 930B and the latch circuit 950B can be used to count and store the number of oscillations of the second ring circuit during each sampling period, respectively. As previously mentioned, the number of oscillations at the second ring circuit can change across sampling periods based on the first set of parameters other than the parameters of interest because the second ring circuit does not include a parameter-based delay circuit. Therefore, the output of the latch circuit 950B can be a nearly continuous representation of the behavior of the second ring circuit relative to the first set of parameters. In some variations, the second ring circuit oscillates at a rate between 30 MHz and 60 MHz (e.g., varying by + / - 20% from die to die, varying by + / - 20% based on voltage and temperature, etc.). In some variations, such as, for example, where the first set of parameters includes temperature, multiple sampling periods can be averaged (e.g., total count of oscillations within a range of sampling periods / number of sampling periods within the range of sampling periods) because temperature typically changes relatively slowly relative to the sampling rate. In some variations, the delay circuit 910B may include a set of inverters; in some variations, the set of inverters may be coupled to a multiplexer. In some variations, the set of inverters is in a closed loop configuration with positive feedback. In some variations, the second loop circuit may include one or more of a resistor-capacitor delay circuit, a resistor-inductor delay circuit, and a capacitive delay circuit.

[0111] Fig.10 A schematic diagram of a sensor 1000 including two ring oscillator circuits (e.g., oscillator circuits 900A and 900B) is shown, which utilizes comparison of counts to determine a parameter of interest. The output of sensor 1000 may be a digital signal, and there is no need to include an ADC in sensor 1000 (which may save space and / or reduce size). In some variations, sensor 1000 may be on a single chip. Sensor 1000 may include a first ring circuit (i.e., oscillator circuits 900A and 900B) oscillating at a first rate (e.g., 100 MHz). Fig.10 Ring #1 in (similar to Fig. 9A The first loop circuit) and the second loop circuit (ie, Fig.10 Ring #2 in (similar to Fig. 9BThe second rate may vary based on a first set of parameters (e.g., temperature and voltage) other than the parameter of interest (e.g., pressure), and the first rate may vary based on the first set of parameters and the parameter of interest. Similarly stated, the second rate may vary based on a set of parameters, and the first rate may vary based on a different set of parameters. As mentioned above, ring #1 and ring #2 may be on the same die. Thus, at least some of the physical parameters (e.g., the first set of parameters) of the two rings will have substantially (e.g., within 1%, within 2%, within 5%, within 10%, within 25%) the same variations (e.g., same silicon process variations, same voltage variations, same temperature variations, etc.). In some variations, ring #1 and #2 may be on different dies.

[0112] Still reference Fig.10 , an input clock signal (e.g., a 32,768 Hz input clock; i.e., an input clock) may be input into the divider circuit 1010, where the divider circuit 1010 may output a signal having a predetermined sampling rate (e.g., 200 Hz, 256 Hz, etc.). The signal having the predetermined sampling rate may then be input into the first rate counter circuit 1030A, the first latch circuit 1050A, the second rate counter circuit 1030B, and the second latch circuit 1050B. For each sampling period, the first rate counter circuit 1030A may count the number of oscillations at ring #1 during the sampling period, and the second rate counter circuit 1030B may count the number of oscillations at ring #2 during the sampling period. The first latch circuit 1050A may store a first count value from the first rate counter circuit 1030A at each sampling period, and the second latch circuit 1050B may store a second count value from the second rate counter circuit 1030B at each sampling period. For each sampling period, the parameter of interest calculator circuit 1070 (e.g., a third circuit) may receive (1) a first count value from the first latch circuit 1050A (counted by the first rate counter circuit 1030A) during that sampling period, and (2) a second count value from the second latch circuit 1050B (counted by the second rate counter circuit 1030B) during that sampling period. The parameter of interest calculator circuit 1070 may then use both the first count value and the second count value to determine a value of the parameter of interest (e.g., a pressure value) (e.g., represented as a third signal). In some variations, the parameter of interest calculator circuit 1070 may use one or more lookup tables to determine the value of the parameter of interest. In some variations, the parameter of interest calculator circuit 1070 may use an equation that is a function of both the first count value and the second count value to determine the value of the parameter of interest. In some variations, the functionality of the parameter of interest calculator circuit 1070 may be performed on a separate chip, such as Fig.11A or Fig. 11BIn some variations, the first count value may be modified based on the second count value to determine the value of the parameter of interest.

[0113] although Fig.10 Two ring oscillator circuits are shown (i.e., Ring #1 and Ring #2), but in some variations, more than two ring oscillator circuits may be used. In some variations, one or more additional (e.g., a third ring oscillator circuit, a fourth ring oscillator circuit, etc.) Fig.10 Sensor 1000 is shown. For example, in some variations, multiple (e.g., two, three, four, or more) ring oscillator circuits similar to Ring #1 may be used to allow for the same as described above with respect to Fig.10 The value of another parameter of interest is determined in a similar manner. Fig.10 A first rate counter circuit 1030A, a first latch circuit 1050A, a second rate counter circuit 1030B, and a second latch circuit 1050B are shown, but in some variations any number (e.g., one, three, six, eight, etc.) of rate counter circuits and / or latch circuits may be used. For example, in some variations, the sensor 1000 may also include a third ring oscillator circuit that may include a parameter-based delay element that changes delay at a different rate than, for example, other elements in the first ring oscillator circuit, the second ring oscillator circuit, and / or the third ring oscillator circuit. The difference in count values ​​between the additional (e.g., third, fourth, etc.) ring oscillator circuits and the first ring oscillator circuit and / or the second ring oscillator circuit may be used to determine the value of another parameter of interest (e.g., force, light amplitude, audio amplitude, radiation, resistance or capacitance corresponding to a chemical or physical reaction, etc.). In some variations, the die temperature may be measured or otherwise determined using a difference in count values ​​between an additional (eg, third) ring oscillator circuit and the first ring oscillator circuit and / or the second ring oscillator circuit.

[0114] In some variations, pulse time delay measurements may be used to determine the temperature of the first ring oscillator circuit or the second ring oscillator. For example, the time of a pulse or known voltage may be measured, and if the voltage is tightly controlled, an assumption may be made that for other pulses, the time will differ only based on temperature.

[0115] The various circuits discussed herein may be included on any number of chips, dies, and / or substrates. In some variations, the various circuits discussed herein may be included across multiple chips, dies, and / or substrates. Fig.11AA schematic diagram of a sensor 1100A including a sensor chip 1120A and a computing device, which in this example is a microcontroller chip 1130A, is shown. The output of the sensor 1100A may be a digital signal, and there is no need to include an ADC in the sensor 1100 (which may save space and / or reduce size). The circuitry of the sensor chip 1120A may be similar to Fig.10 sensor 1000, but may include serializer circuitry 1110A in place of the Fig.10100A). The serializer circuit 1110A may receive a first count value of ring #1 from the first latch circuit and a second count value of ring #2 from the second latch circuit for each sample, and provide a serialized representation of the two count values ​​to the output circuit 1140A. The serializer circuit 1110A may be electrically coupled to the output circuit 1140A via a wire (e.g., at least 10 cm long, at least 20 cm long, at least 30 cm long, at least 40 cm long, at least 50 cm long, at least 100 cm long, between about 50 cm and 100 cm). In some variations, the output circuit 1140A is a universal asynchronous receiver-transmitter (UART). The output from the output circuit 1140A may be provided to a parameter of interest calculator circuit 1170A, which may use the output signal from the serializer circuit 1110A to determine the value of the parameter of interest. In some variations, the sensor chip 1120A may include input / output (I / O) for power, ground, and clock. In some variations, power may be extracted from the clock to power the sensor chip 1120A. In some variations, the sampling rate may be 256 Hz, and the serializer 1110A may output any suitable number of bits per sampling cycle, such as, for example, 38 bits or 40 bits per sampling cycle. In some variations, ring #1 may include one or more (e.g., two, three or more) inverters and a resistor capacitor (RC) circuit, wherein a piezoresistive element changes a resistor in the RC circuit. The piezoresistive element may have a resistance between 1999.88 ohms per mmHg and 2000.12 ohms per mmHg and a 5pF capacitor, wherein the delay results in a first rate of 90 MHz to 100 MHz. In some variations, the parameter of interest calculator circuit 1170A may use a rolling average (e.g., a one-second rolling average) of the count values ​​from ring #2 (e.g., instead of the count value from a single sampling cycle). In some variations, the sensor chip 1120A may communicate wirelessly with the microcontroller chip 1130A. In some variations, the sensor chip 1120A may communicate with the microcontroller chip 1130A via a wired connection (rather than wirelessly). In some variations, the sensor includes a first circuit (e.g., an oscillator circuit 900A) configured to receive an input clock signal and output a first output count signal at a predetermined sampling rate (e.g., 200 Hz, 250 Hz, etc.). The sensor may also include a second circuit (e.g., an oscillator circuit 900B) configured to receive an input clock signal and output a second count signal at a predetermined sampling rate.The sensor may further include a third circuit coupled to the first circuit and the second circuit (e.g., the parameter of interest calculator circuit 1070, the sensor chip 1120A, the microcontroller chip 1130A, the output circuit 1140A, the parameter of interest calculator 1170A). The third circuit may be configured to generate a third signal (e.g., representing the value of the parameter of interest) based on the first output count signal and the second output count signal.

[0116] Fig.11A and Fig. 11B An exemplary circuit diagram for measuring a parameter using two oscillator rings is shown. Fig.11A and Fig. 11B As shown, ring #1 is set to oscillate at a relatively high frequency, and may be in the range of, for example, about 50 MHz to about 100 MHz. The rate at which ring #1 oscillates may be affected by several factors, such as, for example, the temperature of the die, the supply voltage, and the intrinsic speed of the silicon, which may vary, for example, by + / -20% between different silicon dies from different wafers.

[0117] The sensor delay may vary depending on the property being measured. In the example configuration where the sensor delay varies depending on pressure, by including a piezoresistive pressure sensitive cell within the die, pressure may also affect the oscillation rate of ring #1. Thus, a change in pressure directly results in a change in the oscillation rate of ring #1 only. Note that oscillating ring #2 is configured to have no change with respect to changes in pressure (since there is no sensor delay component).

[0118] A precise low-speed input clock such as 32.768 kHz may be divided to produce a sampling rate such as 200 Hz (e.g., as Fig.11A ) or 256 Hz (e.g. Fig. 11B ). The oscillation of the ring may cause a counter to increment, and at the sampling rate, the count value may be latched and the counter may be reset to 0. Thus, at the end of each sampling period, the latch may contain the number of oscillations of the ring during the last sampling period. For example, for a 256 Hz sampling rate, the ring may oscillate hundreds of thousands of times. To measure blood pressure in the range of -50 mmHg to +300 mmHg, only 1400 quantization levels may be needed (e.g., required) to achieve a 0.25 mmHg resolution. 1400 quantization levels is a small fraction of the 400,000 clocks typically counted during a sampling period, and the resolution of the sensor need only result in a change in a few counts of the counter. Note that for a 100 MHz oscillation rate, 1 count is only 10 nanoseconds. Therefore, a 1 mmHg pressure change only needs to result in a delay time change of 50 nanoseconds to 100 nanoseconds.

[0119] Fig.11A and Fig. 11BRing #2 in may be configured to latch at the same rate as ring #1, but because ring #2 does not have a piezoresistive element (i.e., sensor delay) as part of its structure, the oscillation rate of ring #2 may be insensitive or agnostic to changes in pressure. Thus, the oscillation rate of ring #2 may be affected only by, for example, temperature, voltage, and intrinsic properties of silicon. As the temperature of the die increases, the oscillation rate will slow down, and as the temperature decreases, the oscillation rate will speed up. Similarly, as the voltage increases, the oscillation rate will increase, and as the voltage decreases, the oscillation rate will decrease. Because ring #2 is on the same silicon die as ring #1, the temperature and voltage may be the same, and the variations due to temperature and voltage may be the same as those of ring #1. The changes in the latched values ​​of ring #2 may then be used when calculating the sensed property measured by ring #1. Thus, ring #2 may act like a continuous calibration of the sensor die, where recalibration is performed at the sampling rate.

[0120] In variations where the sensors described herein are used to measure pressure in a clinical setting, a system or medical device having a pressure sensor may be "tare" (zeroed) prior to insertion into the body. The system or device may then be configured to determine and / or store the clock rates of both loops. When the sensor is placed in the body, the temperature may rise, and the operation of loop #2 may slow down. The amount by which the operation of loop #2 slows down may be incorporated into the calculation used to convert the loop #1 rate to pressure.

[0121] While any clock may be used for the low speed input clock, in some variations a 32.768 kHz clock may be desired. For example, in variations where accuracy is particularly desired, as the sensors described herein may utilize a clock derived from a crystal. These crystals routinely achieve an accuracy of + / - 5ppm (0.0005%), so the use of these crystals will add only a small error (which may be essentially insignificant (estimated to be within 0.5 mmHg for a pressure sensor)).

[0122] Once two counter values ​​are latched, a small area on the die can be used to transmit those values ​​as digital outputs (e.g., digital communication packets). In some variations, these values ​​can be sent as serial packets that can be directly read by a computing device (e.g., microcontroller 1130A or 1130B). In some variations, a universal asynchronous receiver transmitter (UART) protocol can be utilized. The UART protocol supports communication packets that can be as short as 1 byte and up to several thousand bytes. As an example, in a variation in which each counter is 19 bits, only 38 bits need to be transmitted, which can be suitable for simple 5-byte (40-bit) packets. Although UART is discussed herein and can be utilized in some variations, in other variations, other communication protocols can be used as an alternative or supplement to UART.

[0123] At least some variations described herein may utilize two or more rings and use a computing device to perform runtime calibration.

[0124] While the above examples involve pressure measurements, the same general techniques can measure other physical properties such as force, light amplitude, acoustics, or electrochemical reactions. Sensor delays can result in measurable changes in impedance, capacitance, or inductance; additionally, sensor delays can result in changes in the speed of propagation of the electrical signal within the loop.

[0125] One benefit of this sensor arrangement is that the die is not limited to 2 rings. For example, in some variations, the sensor described herein may include a third ring having an oscillation rate that can be modified by different physical properties. For example, the third ring may be set to have additional sensitivity to temperature (relative to ring #2), and thus can provide a highly accurate report of the patient's core temperature. A fourth ring may be used, which has an oscillation rate that can be based on electrochemical properties such as pH changes. At higher sampling rates, it is possible to pick up acoustic markers associated with the opening / closing of the heart valve. In each of these variations, the analog signal can be converted to digital data, which can be transmitted via a single wire using a digital message. Additional sensing may only require slightly larger messages. For example, at a 256Hz sampling rate and a 32.768kHz input clock, a single output wire can transmit 128 bits during each sampling cycle. This can accommodate 5 different sensors, each with 19-bit resolution. If greater resolution or higher sampling rates are desired, the clock rate can be doubled or one or more additional wires can be added. The ability to move from analog to digital signaling has a huge impact on signal fidelity, interoperability with existing patient monitoring equipment, and miniaturization of SSPT devices, and has applications across many aspects of patient care, especially in long-term point-of-care (PFC) where size and power requirements are extremely important.

[0126] It can be seen that Fig. 11B A sensor chip 1120B and a microcontroller chip 1130B are shown. The sensor 1110B is substantially similar to Fig.11A Sensor 1100B uses a 256 Hz sampling rate, while sensor 1100A uses a 200 Hz sampling rate. Fig.11A The serializer 1110A is shown as being separate from the two latches, but from Fig. 11B The latch serializer 1110B may be from Fig.11A Of course, the 200 Hz and 256 Hz sampling rates are examples, and some variations may use different sampling rates.

[0127] In some variations, the start and stop bits may be latched directly into the shift register. Fig.13A An example of a latch serializer communicatively coupled to two 19-bit counters is shown (e.g., similar to Fig. 11B The latch serializer 1110B in is similar to Fig.11A 110A and two latches coupled to the serializer 1110A, and so on). Fig.13A In the example shown, the 32.768kHz input clock is divided into a 256Hz latch signal and a 16,384Hz shift signal. The 47-bit latch shift register receives a 1 shift-in signal, a latch signal, and a shift signal, as well as the value, start bit, and stop bit from each of the two 19-bit counters. In this variation, the 47-bit latch shift register outputs a UART-type serial output. Based on the 256Hz latch signal, the counter value and the UART start bit ("0") and stop bit ("1") are directly latched into the 47-bit output shift register in the correct order. The shift register is "shifted" based on a 16,384Hz clock. This will generate 64 bits (16,384 bits / 256=64) during each sampling period in a 1 / 256Hz sampling period. After the first 47 bits are transmitted, because "1" is shifted in, the next 17 bits transmitted will all be 1. These "1"s properly complete byte 5 (including its stop bit) and produce 14 idle ("1") bits before the next frame. Fig. 13B A UART type serial output is shown in . Each frame has a certain number of bytes, with no delay between each byte. During the idle time between frames, in some variants, the digital output may be high (indicated by 1). In some variants, each data byte is preceded by a single start bit (e.g., low) and a single stop bit (e.g., high). In some variants, the individual data bits within a byte are transmitted in a most significant bit first manner. In one example, the 5 bytes within a frame may be: (1) Byte 1: Bit 7 = Ring #1 count bit 18; Bit 6 = Ring #1 count bit 17; ...; Bit 0 = Ring #1 count bit 11; (2) Byte 2: Bit 7 = Ring #1 count bit 10; Bit 6 = Ring #1 count bit 9; ...; Bit 0 = Ring #1 count bit 3; (3) Byte 3: Bit 7 = Ring #1 count bit 2; Bit 6 = Ring #1 count bit 1; Bit 5 = Ring #1 count Byte 0; Bit 4 = Ring #2 Count Bit 18; Bit 3 = Ring #2 Count Bit 17; ...; Bit 0 = Ring #2 Count Bit 14; (4) Byte 4: Bit 7 = Ring #2 Count Bit 13; Bit 6 = Ring #2 Count Bit 12; ...; Bit 0 = Ring #2 Count Bit 6; (5) Byte 5: Bit 7 = Ring #2 Count Bit 5; Bit 6 = Ring #2 Count Bit 4; ...; Bit 2 = Ring #2 Count Bit 0; Bit 1 = Always 1; Bit 0 = Always 1. Figure 13 and Fig. 13BOne benefit of the variation shown is that no state machine is required (eg, to keep track of byte or packet boundaries).

[0128] In one example, the rate of serial output can be half of the input clock. In one example, a single trigger can be used to generate a 16,384kHz clock, and a 6-flip-flop divider of the 16,384kHz clock is used to obtain a 256Hz sampling rate. At each sample boundary, the value from the two counters can be latched. In some variations, instead of building a state machine to process the start / stop bit, 38 counter bits (2×19) and the start / stop bit can be directly latched into a single 47-bit shift register. In one example, the shift register only needs to be 47 bits (rather than 50 bits) because there are 10 bits per byte, but the last 3 bits of byte 5 are always 1. At the output clock rate (16,384kHz), the bit from the shift register is shifted out and "1" is shifted in at the other end. This will force "1" as output during the time between 5 bytes.

[0129] b. Output devices

[0130] In general, an output device as described herein may be configured to output a signal corresponding to a measurement parameter as described herein. For example, the output signal may be a digital signal, so that a circuit such as an ADC is not required, thereby reducing device complexity. In some variations, the controller 320 may include an output device 328 configured to output the third signal 532 as a digital signal. For example, the output device 328 may be configured to output the third signal 532 as a set of binary coded bits at a periodic rate. In some variations, the output device 328 may include one or more of a wire configured for wired transmission and an antenna configured for wireless transmission. In some variations, the third signal 532 may be encoded and / or output on a separate wire to increase noise immunity.

[0131] As described herein, the measurement parameter may be represented by 4,096 quantization levels, which may be transmitted as a digital signal using 12 bits at a predetermined rate (e.g., once every 5 milliseconds, 3,200 bits per second). It should be appreciated that transmission speeds below 5,000 bits per second have high noise reliability because each bit is long enough so that noise bursts are shorter than individual bit times.

[0132] In some variations, the digital signal includes one or more of standard binary encoding (e.g., UART), pulse width modulation (PWM), Manchester encoding, etc. In some variations, the output device may include a universal asynchronous receiver-transmitter (UART). Therefore, the output device may not have a PGA and / or ADC, thereby reducing component count and reducing manufacturing complexity. In some variations, the digital signal can be output using one or more of a wire and an antenna. There are several methods for providing a binary coded value on a single wire, including standard NRZ or NRZI UART technology, which has a start bit, 8 coded bits, and a stop bit. In some variations, the digital signal can be output as ASCII text and / or grayscale encoding of multiple bytes.

[0133] In some variations, the output device may include a serializer (e.g., serializer circuitry 1120), where the serializer may include circuitry configured to convert parallel data to serial data and / or vice versa. In some variations, the output device may include an output register, where the output register may include circuitry having a flip-flop and configured to store data.

[0134] c. Processor

[0135] like Figure 3 As depicted, the sensor system 300 may include a processor 322 and a machine-readable memory 324 (e.g., collectively referred to as a controller) in communication with one or more computing devices 340. The processor 322 may be connected to the computing device 340 via a wired or wireless communication channel. The processor 322 may be configured to control one or more components of the sensor system 300, such as the communication device 330. The processor 322 may be implemented consistent with numerous general or special-purpose computing systems or configurations. Various exemplary computing systems, environments, and / or configurations that may be suitable for use with the systems and devices disclosed herein may include, but are not limited to, software or other components within or embodied on a personal computing device, a network appliance, a server or server computing device (such as a routing / connectivity component), a portable (e.g., handheld) or laptop device, a multiprocessor system, a microprocessor-based system, and a distributed computing network.

[0136] The processor 322 may combine data received from the memory 324 and the computing device 340 to control the system 300. The memory 324 may further store instructions for the processor 322 to execute modules, processes, and / or functions associated with the system 300 and / or the computing device 340. The processor 322 may be any suitable processing device configured to run and / or execute a set of instructions or codes, and may include one or more microcontrollers, data processors, image processors, graphics processing units, physical processing units, digital signal processors, and / or central processing units. The processor 322 may be, for example, a general-purpose processor, a field programmable gate array (FPGA), an application-specific integrated circuit (ASIC), which is configured to execute application processes and / or other modules, processes, and / or functions associated with the system and / or a network associated therewith. For example, the processor 322 may be a dual-core microcontroller. The underlying device technology of various component types may be provided, such as metal oxide semiconductor field effect transistor (MOSFET) technology (like complementary metal oxide semiconductor (CMOS)), bipolar technology, polymer technology (e.g., silicon conjugated polymer and metal conjugated polymer-metal structure), hybrid analog and digital, combinations thereof, and the like.

[0137] d. Memory

[0138] Some variations of the memory 324 described herein involve a computer storage product having a non-transitory computer-readable medium (also referred to as a non-transitory processor-readable medium) having thereon instructions or computer code for performing various computer-implemented operations. A computer-readable medium (or processor-readable medium) is non-transitory in the sense that it does not itself include a transient propagating signal (e.g., a propagating electromagnetic wave that carries information over a transmission medium such as air or a cable). The medium and computer code (also referred to as code or algorithm) may be one designed and constructed for one or more specific purposes. Examples of non-transitory computer-readable media include, but are not limited to, flash memory, non-volatile memory (e.g., Optane TM , 3D XPoint TM), magnetic storage media such as hard disks, floppy disks, and magnetic tapes; optical storage media such as compact disks / digital video disks (CD / DVD), compact disk-read only memory (CD-ROM), and holographic devices; magneto-optical storage media such as optical disks; solid-state storage devices such as solid-state drives (SSDs) and solid-state hybrid drives (SSHDs); carrier signal processing modules; and hardware devices that are specifically configured to store and execute program code, such as application specific integrated circuits (ASICs), programmable logic devices (PLDs), read-only memories (ROMs), and random access memory (RAM) devices. Other variations described herein relate to computer program products that may include, for example, instructions and / or computer code disclosed herein.

[0139] The systems, devices, and / or methods described herein may be implemented by software (implemented on hardware), hardware, or a combination thereof. Software modules (implemented on hardware) may be expressed in a variety of software languages ​​(e.g., computer code), including C, C++, Python, Ruby, Visual and / or other object-oriented, procedural or other programming languages ​​and development tools. Examples of computer code include, but are not limited to, microcode or microinstructions, machine instructions (such as generated by a compiler), code for generating network services, and files containing high-level instructions executed by a computer using an interpreter. Additional examples of computer code include, but are not limited to, control signals, encrypted code, and compressed code.

[0140] e.Communication equipment

[0141] In some variations, the sensor system 300 described herein can communicate with one or more of the blood control device, network and computer system through the communication device 330. In some variations, the sensor system 300 can communicate with other devices (e.g., computing devices) via one or more wired and / or wireless networks. A wireless network can refer to any type of digital network that is not connected by any type of cable. Examples of wireless communications in a wireless network include, but are not limited to, Bluetooth, cellular, radio, satellite and microwave communications. However, a wireless network can be connected to a wired network to connect to the Internet, other carrier voice and data networks, business networks and personal networks. Wired networks are usually carried by copper twisted pairs, coaxial cables and / or fiber optic cables. There are many different types of wired networks, including wide area networks (WANs), metropolitan area networks (MANs), local area networks (LANs), Internet (IANs), campus networks (CANs), global area networks (GANs) (such as the Internet), and virtual private networks (VPNs). In the following, a network refers to any combination of wireless, wired, public and private data networks that are usually interconnected by the Internet to provide a unified networking and information access system. In some variations, any data stored in memory 324 may be transmitted using communication device 330 .

[0142] Cellular communications may encompass technologies such as GSM, PCS, CDMA or GPRS, W-CDMA, EDGE or CDMA2000, LTE, WiMAX, and 5G network standards. Some wireless network deployments combine networks from multiple cellular networks or use a mix of cellular, Wi-Fi, and satellite communications. In some variations, the network interface may include a radio frequency receiver, a transmitter, and / or an optical (e.g., infrared) receiver and transmitter. The communication device 330 may communicate with one or more components of the system 300 by wire and / or wirelessly.

[0143] II. Sensor housing

[0144] The sensors described herein may be housed in, positioned within, and / or encapsulated in a sensor housing and integrated into an elongated body (e.g., a catheter) used in various devices (such as, for example, blood flow control devices and pressure monitoring devices), as further described below. The sensor may monitor physiological conditions during medical procedures and / or monitor patient physiological functions during routine and critical medical care. In some variations, the sensor housing may be a tubular member that includes an opening (e.g., a window) configured to expose the sensor to the surrounding environment (e.g., blood within a blood vessel) and / or one or more struts that assist in attaching the sensor housing (and therefore the sensor) to the elongated body. In some variations, the sensor housing may be coupled to or otherwise attached to a sleeve. The sleeve may be positioned around the elongated body or otherwise surround the elongated body, thereby coupling the sensor to the elongated body. Depending on the number of sensors included in the elongated body, one or more sensor housings may be integrated into the elongated body. In another variation, the sensor and / or sensor housing may be configured to be small in size (e.g., having a small diameter) so that the sensor can be integrated into an elongated body (e.g., a catheter) for advancement into a blood vessel or through an arterial or venous catheter (e.g., an arterial or venous access line). The sensor housing may be configured to protect the sensor from damage due to moisture or fluid intrusion (e.g., upon exposure to blood), and / or to protect the sensor from pressurization (e.g., pressure from a balloon of a blood flow control device).

[0145] The sensor housing may be formed of any suitable biocompatible material. For example, in some variations, the sensor housing may be formed of a polymer such as, for example, polytetrafluoroethylene (PTFE), polyimide, Thermoplastic polymers, combinations thereof, and the like. Exemplary thermoplastic polymers may be polycarbonate, polycarbonate / acrylonitrile-butadiene-styrene terpolymer blends, and the like. In some variations, the sensor housing may be formed of a metal (e.g., stainless steel), a bondable metal alloy, or a combination thereof. In one variation, the sensor housing comprises stainless steel. In variations in which each of the sleeve and the sensor housing comprises a metal (e.g., stainless steel) tube, the tubes may be laser welded together, and an opening may be cut through the tubular walls of both the sleeve and the sensor housing to expose the sensor or otherwise provide access to the sensor.

[0146] In some variations, as mentioned above, the sensor may be fully or partially encapsulated in a sensor housing. The sensor may be encapsulated using, for example, various polymers. Encapsulating the sensor in a housing may make the sensor reading less susceptible to changes in bending forces acting on the sensor, and / or may help isolate the sensor from pressurization effects when using a pressurized device to, for example, measure, monitor, and / or adjust blood pressure. Encapsulating the sensor fully or partially in a polymer may also act as a sealant and protect the electrical components of the sensor from moisture or fluid intrusion. Therefore, encapsulation in a polymer may make the sensor readings more consistent. In some variations, the sensor may be fully or partially encapsulated in a metal (e.g., stainless steel) housing in RTV (room temperature vulcanized) silicone.

[0147] Exemplary polymers for fully or partially encapsulating the sensor include, but are not limited to, hydrophobic polymers such as RTV silicone, polytetrafluoroethylene (PTFE), polyimide, and And combinations thereof. In one variation, encapsulating the sensor may include: forming a polymer layer in the sensor housing, such as a layer containing RTV silicone or a different polymer, placing the sensor on the polymer layer, and then curing the polymer. Next, the sensor may be encapsulated by covering the sensor with an additional polymer (e.g., RTV silicone) and then curing the polymer. The polymer may have a compliance that allows a pressure signal to be transmitted through the polymer, so that physiological conditions such as, for example, pressure can be transmitted to the sensor through the polymer. In some variations, a separate seal (e.g., an epoxy seal) may be provided in the sensor housing to protect the sensor from pressurization. Instead of encapsulating the sensor, the polymer described herein may also be used to coat the sensor and any associated components (e.g., wires, wire pads). In variations in which the sensor is not encapsulated, the previously mentioned polymer may be used to adhere the sensor to the sensor housing, or the sensor may be fixed to the sensor housing using an adhesive.

[0148] The sensor housing may have any suitable size, shape, and geometry. For example, the sensor housing may have a tubular, rectangular, square, or oval shape. In one variation, the sensor housing may be tubular in shape and include an opening (e.g., a window) as mentioned above. The sensor housing may be sized so that the sensor fits tightly within the sensor housing, thereby minimizing space utilization on the elongated body.

[0149] A. Tubular sensor housing

[0150] As mentioned above, in some variations, the sensor housing may include a tubular shape. In these variations, the inner diameter of the sensor housing may be about 0.01 inches to about 0.04 inches, including all values ​​and subranges therein. In some variations, the inner diameter of the sensor housing may be, for example, about 0.012 inches (0.30 mm) to about 0.035 inches (0.89 mm), about 0.015 inches (0.38 mm) to about 0.03 inches (0.76 mm), about 0.017 inches (0.43 mm) to about 0.025 inches (0.64 mm), or about 0.019 inches (0.48 mm) to about 0.022 inches (0.56 mm), including all values ​​and subranges therein. In one variation, the inner diameter of the sensor housing may be about 0.02 inches (0.51 mm). In some variations, the outer diameter of the sensor housing may be about 0.02 inches (0.51 mm) to about 0.08 inches (2.0 mm), including all values ​​and subranges therein. In some variations, the outer diameter of the sensor housing may be, for example, about 0.021 inches (0.53 mm) to about 0.06 inches (1.5 mm), about 0.022 inches (0.56 mm) to about 0.04 inches (1.0 mm), about 0.023 inches (0.58 mm) to about 0.03 inches (0.76 mm), about 0.024 inches (0.61 mm) to about 0.027 inches (0.69 mm), including all values ​​and subranges therein. In one variation, the outer diameter of the sensor housing may be about 0.025 inches (0.64 mm).

[0151] 17A to 17C An exemplary tubular sensor housing is shown. 17A to 17C , the sensor 1700 may be disposed within a tubular sensor housing 1702. The sensor 1700 may include a MEMS piezoresistive sensor 1700a on a CMOS bare die 1700b. A window 1704 formed through the wall of the tubular sensor housing 1702 may expose the sensor 1700 to an external environment (e.g., blood flowing through an artery or vein). Fig. 17CAs shown in the cross-sectional view of FIG. 1704 , the sensor 1700 may be sized so that the sensor 1700a and the die 1700b fit tightly within the inner cavity 1706 of the tubular sensor housing 1702. An adhesive (e.g., an RTV adhesive) may be included in the tubular sensor housing 1702 (e.g., under the sensor 1700) to secure the sensor 1700 to the tubular sensor housing. In some variations, an adhesive may also be included to partially or completely encapsulate the sensor 1700 in the tubular sensor housing 1702. Wire bonding pads 1708 for connecting to the CMOS circuitry 1710 on the sensor 1700 may be fed through the window 1704 and then coated (or encapsulated) with an adhesive (e.g., an adhesive used to encapsulate or attach the sensor 1700 to the tubular housing 1702).

[0152] housed in a tubular sensor housing (e.g. 17A to 17C The sensor within the housing (of the embodiment of the present invention) may have any width and thickness that allows it to be incorporated into the sensor housing and / or the elongated body, and may vary depending on the parameter being measured and / or the device in which the sensor is included (e.g., a blood flow control device, a pressure measurement device, other medical or non-medical device that measures one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude). In some variations, the sensor may be configured to have any width, thickness, and height as previously described herein. In other variations, the sensor width may be approximately 330 microns and the sensor thickness may be approximately 250 microns.

[0153] B. Sensor housing with support material

[0154] Some variations of the sensor housing may include one or more structural components configured to couple the sensor housing to an elongated body (e.g., a catheter). The structural component may be configured as a strut having edges that can be used to attach (e.g., weld) the sensor housing to the elongated body. For example, a window of the sensor housing may be aligned with an opening in the elongated body, and the strut may be attached to the elongated body at one or more of the strut edges. The height of the strut may be such that the sensor housing is appropriately positioned within the lumen of the elongated body and relative to the elongated body to minimize interference with external elements that may affect sensor functionality. For example, the sensor may be exposed just enough to obtain accurate sensor measurements, but may be protected from damage by being placed within the sensor housing.

[0155] For example, Fig.18As shown, the sensor housing 1800 may include a body portion 1806, a window 1808, a cutout 1804, and two struts 1802 that may be used to couple the sensor housing 1800 to an elongated body (e.g., not shown). The struts 1802 and the cutouts 1804 on the outside of the struts 1802 may help attach (e.g., laser weld) the sensor housing 1800 to the elongated body. The sensor housing 1800 may have a diameter sized to fit within the elongated body, and in some variations, may have a diameter of about 0.1 Fr to about 5 Fr, including all values ​​and subranges therein. For example, the sensor housing may be about 0.1 Fr, about 0.2 Fr, about 0.3 Fr, about 0.4 Fr, about 0.5 Fr, about 0.6 Fr, about 0.7 Fr, about 0.8 Fr, about 0.90 Fr, about 1 Fr, about 2 Fr, about 3 Fr, about 4 Fr, or about 5 Fr. A sensor housing having a size of about 1 Fr may be used in medical applications, for example, when the sensor is passed through a previously placed arterial or venous catheter.

[0156] C.Sensor sleeve

[0157] In some variations, a sleeve may be used to assist in coupling the sensor housing to an elongated body (e.g., a catheter) of a device (e.g., a blood flow control device). In these variations, the sensor housing may be coupled to or otherwise attached to the sleeve, which may be positioned around the elongated body to partially or completely surround the elongated body, thereby coupling the sensor to the elongated body, as previously described.

[0158] The sleeve can be configured to receive the elongated body, thereby coupling the sensor housing and thus the sensor to or integrating with the elongated body. The sleeve can include an inner cavity configured to receive the elongated body, an opening (e.g., a window) through which the sensor housing can be exposed, and, in some variations, features to promote a gradual stiffness transition between the elongated body and the sleeve.

[0159] In some variations, the sleeve may be sized and shaped such that the elongated body may be received within the sleeve. For example, the sleeve may include an inner cavity therethrough having a cross-sectional shape corresponding to the cross-sectional shape of the elongated body and having a diameter greater than the outer diameter of the elongated body. For example, in some variations, the sleeve may be tubular. In some variations, the sleeve may add stiffness to the elongated body around a sensor housed within the sleeve, thereby protecting the sensor from damage and isolating the sensor from sensitivity-related errors that may occur due to flexing of the elongated body.

[0160] The sleeve can be made of any suitable biocompatible material. For example, the sleeve can be formed of a polymer such as, for example, polytetrafluoroethylene (PTFE), polyimide, Thermoplastic polymers, combinations thereof, and the like. Exemplary thermoplastic polymers may be polycarbonate, polycarbonate / acrylonitrile-butadiene-styrene terpolymer blends, and the like. In some variations, the sleeve may be formed of a metal (e.g., stainless steel), a bondable metal alloy, or a combination thereof. In one variation, the sleeve comprises stainless steel.

[0161] In some variations, the sleeve may include features that can gradually transition the stiffness of the elongated body and distribute the undesirable external forces (e.g., bending forces) acting on the elongated body. For example, in some variations, the sleeve may be harder than the elongated body, and / or the combination of the elongated body and the sleeve together may make the portion of the device with the sleeve harder than the portion of the elongated body without the sleeve. In these variations, the sleeve may include slits and / or openings to facilitate the transition between the portion of the device with and the portion without the sleeve. The slits or openings may be formed in any suitable shape or pattern, such as, for example, in a spiral shape. In some variations, the slits and / or openings may be positioned only in the transition zone on the sleeve (e.g., at one or both ends of the sleeve), while in other variations, the slits and / or openings may be along the entire length of the sleeve. The transition zone may promote a gradual transition from the less rigid elongated body segment to the more rigid sleeve portion. This may particularly provide the benefit of distributing the bending forces when the elongated body is flexed.

[0162] The sleeve may include one or more sleeve openings, in some variations, in which at least a portion of the sensor housing and / or the sensor may be received therein, and a portion of the sensor housing may be exposed and, therefore, at least a portion of the sensor positioned in the exposed sensor housing may be exposed. A portion of the sensor and / or a portion of the sensor housing may be aligned with the sleeve opening to expose the sensor. For example, a portion of the sensor and / or a portion of the sensor housing may be aligned with the sleeve opening along the depth of the sleeve. For example, the portion of the sensor and / or the portion of the sensor housing may be positioned below the sleeve opening and may be axially aligned with the opening. In some variations, a portion of the sensor housing (e.g., a structural component) may traverse the sleeve opening and may be used to fasten the sensor housing to the sleeve.

[0163] The sensor housing and / or sensor may be inserted into the sleeve and / or positioned within the sleeve so that the sensor housing is positioned within the inner cavity of the sleeve. Thus, the sleeve and sensor housing may be configured so that at least a portion of the sensor housing and / or sensor (e.g., the surface of the sensor) may be aligned with the outer surface of the elongated body. In other words, the sensor housing and / or sensor may be embedded in the sleeve at a depth selected to allow the sensor housing and / or sensor to be aligned with the outer surface or sidewall of the elongated body. The sensor housing and / or sensor may be aligned with the outer surface or sidewall of the elongated body so that they are flush. The sleeve opening may allow the sensor to be exposed to conditions within the patient's body in order to obtain measurements while the sensor is still protected within the sensor housing. In some variations, the elongated body may include an elongated body opening, a window, and / or a cavity for receiving the sensor housing.

[0164] In some variations, instead of the window, the sleeve may include one or more sleeve recesses configured to receive at least a portion of the sensor housing therein. When the sleeve is coupled to the elongated body, the sleeve recess may be aligned with the opening and / or window of the elongated body. The sensor housing may be inserted into and / or positioned in the sleeve recess, and then the sleeve recess may be received in the opening and / or window of the elongated body. In this way, the sensor housing may be received in the opening and / or window on the elongated body so that the sensor housing is aligned with the outer surface or sidewall of the elongated body. In some variations, the sensor may not be contained in the sensor housing or encapsulated in the sensor housing. Instead, the sensor may be inserted into and / or positioned in the sleeve so that the sensor is seated in the inner cavity of the sleeve, and at least a portion of the sensor may be aligned with the outer surface of the elongated body. In such variations, an adhesive may be applied along the periphery of the sensor to additionally secure the sensor to the sleeve. For example, the sleeve may also include one or more holes to provide an entry point for applying an adhesive to secure the sensor to the sleeve. In some variations, the one or more holes in the sleeve may be used to provide an entry point for introducing an adhesive in an amount that fully or partially encapsulates the sensor in the sensor housing.

[0165] Fig.19 An exemplary variation of a sensor 1900 and a sensor housing 1902 attached to an elongated body 1904 via a sensor sleeve 1906 is depicted. Fig.19 , the sleeve 1906 may include a sleeve opening 1908 for receiving a portion of the sensor housing 1902 therein and exposing a portion of the sensor 1900 housed in the sensor housing 1902. A portion of the sensor housing 1902 may be inserted into and / or positioned within the sleeve opening 1908, and the remainder of the sensor housing 1902 may be positioned within the inner cavity ( Fig.191904). In this way, the sensing surface of the sensor housing 1902 and / or the sensor 1900 can be aligned with the outer surface or sidewall of the elongated body 1904. As previously described herein, the sensor 1900 can be encapsulated (e.g., completely contained within the polymer) using a polymer (e.g., RTV silicone) or otherwise sealed within the sensor housing 1902 to make the sensor readings less susceptible to changes in bending forces acting on the sensor, and / or to protect the electrical components of the sensor from moisture, fluid intrusion, etc. In some cases, a hydrophobic polymer coating (e.g., a polyparaxylene coating) can be applied to prevent moisture and / or fluid intrusion. The physiological condition that the sensor is configured to measure can be transmitted to the sensor 1900 through the polymer.

[0166] method

[0167] Also described herein are methods for measuring physical properties using the devices and systems described herein. Specifically, the systems, devices, and methods described herein can be used to accurately measure parameters with a small number of steps and in a compact circuit configuration form factor. Generally speaking, the methods described herein include using an input clock signal and an adjustable delay to generate a plurality of output clock signals. The difference between the output clock signals corresponds to the measured parameter.

[0168] Figure 6 A flow chart describing a variation of a method 600 for measuring parameters is depicted. Figure 6 In the depicted variation, method 600 of measuring a parameter may include, at step 602 , receiving an input clock signal.

[0169] In step 604, the adjustable delay may be used to generate a first output clock signal having a predetermined ratio between the input clock signal and the first output clock signal. In some variations, the frequency of the first output clock signal may be greater than the frequency of the input clock signal.

[0170] In step 606, the second output clock signal may be generated using the adjustable delay. In some variations, the frequency of the second output clock signal may be greater than the frequency of the input clock signal.

[0171] In some variations, the first output clock signal may be varied based on a first set of parameters, and the second output clock signal may be varied based on a second set of parameters different from the first set of parameters. For example, the second set of parameters may include the first set of parameters and at least one additional parameter (e.g., a parameter of interest to be measured). In some variations, the first set of parameters may include one or more of temperature and voltage. For example, the second set of parameters includes temperature, voltage, and one or more of: force, pressure, light amplitude, audio amplitude, and resistance or capacitance corresponding to a chemical or physical reaction.

[0172] In step 608, a third signal may be generated based on the difference between the first output clock signal and the second output clock signal. In some variations, the third signal may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.

[0173] Optionally, the third signal may be output as a digital signal in step 610. For example, the third signal may be output as a set of binary coded bits at a periodic rate.

[0174] Optionally, in step 612, the method may include generating a fourth output clock signal using the adjustable delay, and optionally, in step 614, the method may further include generating a fifth signal based on a difference between the first output clock signal and the fourth output clock signal. In some variations, the fifth signal may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.

[0175] Optionally, in step 618, the method may further include: outputting the fifth signal as a digital signal. For example, the fifth signal may be output as a set of binary coded bits at a periodic rate.

[0176] Fig.12 A flow chart of an illustrative method 1200 for determining a value associated with a physical parameter of interest at a sensor is depicted. In step 1202, a first count number is obtained indicating a number of oscillations at a first ring oscillator circuit during a sampling period. The first ring oscillator circuit may be associated with (e.g., included in) a sensor and may oscillate at a first oscillation rate. The first oscillation rate may be based on a first set of physical parameters and a second physical parameter (i.e., the physical parameter of interest). In step 1204, a second count number is obtained indicating a number of oscillations at a second ring oscillator circuit during the sampling period. The second ring oscillator circuit may be associated with (e.g., included in) a sensor and may oscillate at a second oscillation rate (e.g., different from the first oscillation rate). The second oscillation rate may be based only on a first set of physical parameters, the first set of physical parameters not including the second physical parameter. The first ring oscillator circuit may include a parameter-based delay circuit associated with the second physical parameter, while the second ring oscillator circuit does not include a parameter-based delay circuit associated with the second physical parameter. In step 1206, a value associated with a second physical parameter at the sensor is determined based on the first count number and the second count number.

[0177] Another method involves as in e.g. Fig.14A and Fig. 14BDaisy chaining discussed at . In some variations, the method described herein may include: using a first sensor (e.g., sensor 1402) to measure a first value (e.g., a pressure value) of a first parameter (e.g., pressure); and sending the first value to a second sensor (e.g., sensor 1404) coupled to the first sensor. The method may also include: using a second sensor to measure a second value (e.g., a pressure value, a force value, etc.) of a second parameter (e.g., pressure, force, etc.) that may be the same or different from the first parameter; and generating a serial value including the first value and the second value. For example, the serial value may be a cascade of representations of the first value and the second value. In some variations, the serial value may be a first serial value, and the method may also include: sending the first serial value to a third sensor (e.g., sensor 1406) coupled to the second sensor; using a third sensor to measure a third value (e.g., a pressure value, a force value, a light value, etc.) of a third parameter (e.g., pressure, force, light, etc.) that may be the same or different from one or more of the first parameter and the second parameter; and generating a second serial value including the first serial value and the third value. In some variations, the method may further include: sending the first serial value and / or the second serial value to a computing device, the computing device being configured to determine the first value, the second value, the third value, etc. based on the serial output. In some variations, the first sensor and the second sensor may be operatively coupled to the computing device via only four signals, the four signals being a power signal (e.g., Fig.14A VCC in), clock signals (e.g. Fig.14A CLK in), ground signal (for example, Fig.14A GND in the Fig.14A SER OUT in the .

[0178] Exemplary Sensors

[0179] Fig. 7A is a schematic diagram of an illustrative variation of a sensor 700 including an FPGA circuit and a controller (e.g., a microcontroller). The FPGA circuit may include a first oscillator ring circuit and a second oscillator ring circuit configured to measure pressure. The first oscillator ring circuit may be entirely disposed on a single substrate (e.g., entirely disposed on a single chip) and may be used as a primary offset compensator. The second oscillator ring circuit may include a set of pins (e.g., 2 pins) on the FPGA, wherein a first pin is coupled to a varistor and a second pin input is coupled to the same resistor. The input of the FPGA may be coupled to an input clock signal (e.g., 32.768kHz) output from the microcontroller. The digital output of the FPGA may be coupled to a UART input of the microcontroller.

[0180] Figure 7B can be included in an FPGA (e.g., from Fig. 7AAn example schematic diagram of a circuit system 710 in an FPGA, chip, or the like. The circuit system includes a first oscillator ring circuit (ring #1) and a second oscillator ring circuit (ring #2). The first oscillator ring circuit and the second oscillator ring circuit each oscillate at a respective frequency (e.g., represented by 18 bits, represented by 19 bits, etc.). The difference between the two rings is that ring #2 will oscillate at a rate that depends on an external delay element (whereas ring #1 will not oscillate at a rate that depends on the external delay element), wherein the external delay element is configured to have a delay that varies based on a physical parameter of interest (in this example, applied pressure). The 32,768 Hz clock is (1) divided by 128 in the first clock divider circuit to generate a 256 Hz signal, and (2) divided by 4 in the second clock divider circuit to generate an 8,192 Hz signal. The 8,192 Hz signal can be associated with a shift signal at a 38-bit output register, and the 256 Hz signal can be associated with a latch signal at the 38-bit output register. The 256 Hz signal may also be used to reset the 18-bit counter (eg, at each rising edge or at each falling edge). The 38-bit output register may receive the outputs from the two 18-bit counters and generate a signal for transmission to the UART.

[0181] Figure 7C can be included in an FPGA (e.g., from Fig. 7AAn example schematic diagram of a circuit system 720 in an FPGA, chip, or the like. The circuit system includes a first oscillator ring circuit (ring #1) and a second oscillator ring circuit (ring #2). The first oscillator ring circuit and the second oscillator ring circuit each oscillate at a respective frequency (e.g., represented by 18 bits, represented by 19 bits, etc.). The difference between the two rings is that ring #2 will oscillate at a rate that depends on an external delay element (whereas ring #1 will not oscillate at a rate that depends on the external delay element), wherein the external delay element is configured to have a delay that varies based on a physical parameter of interest (in this example, applied pressure). The 32,768 Hz clock is (1) divided by 128 in the first clock divider circuit to generate a 256 Hz signal, and (2) divided by 2 in the second clock divider circuit to generate a 16,384 Hz signal. The 16,384 Hz signal can be associated with a shift signal at a 48-bit output register, and the 256 Hz signal can be associated with a latch signal at the 48-bit output register. In some implementations, the 48-bit output register has 38 bits associated with two 19-bit counters, which can be formed into five bytes (8 bits per byte) plus a start bit and an end bit for each of the 5 bytes, resulting in 48 bits. The 256 Hz signal can also be used to reset the 19-bit counters (e.g., at each rising edge or at each falling edge). The 48-bit output register can receive the outputs from the two 19-bit counters and generate a signal for transmission to the UART.

[0182] Exemplary Systems and Apparatus

[0183] The systems and devices described herein are not particularly limited and can be used in a variety of industries and applications. For example, the systems and devices can be used with medical devices or otherwise incorporated into medical devices, such as systems and devices for monitoring physiological states and / or physiological conditions in patients during medical procedures. In some variations, these systems may include a device comprising an elongated body (e.g., a catheter) having one or more sensors described herein, which are used to monitor physiological conditions during medical procedures and / or monitor patient physiological functions over an extended period of time during routine and critical medical care. In some cases, these systems may include a blood flow control device. In some variations, these devices can be used to measure (or monitor) blood pressure. In these variations, these devices can be configured to measure blood pressure at any location in the body. For example, these devices can be placed in a central arterial vasculature (e.g., aorta, pulmonary artery) or a central venous vasculature (e.g., vena cava), or in a peripheral arterial vasculature (e.g., femoral artery, radial artery) or a peripheral venous vasculature (e.g., femoral vein, radial vein), and used to measure blood pressure therein. In one variation, these devices can measure blood pressure in the aorta. In other variations, these devices can measure blood pressure in the radial artery. The pressure measurement can be performed with or without a device that includes an expandable member (e.g., an expandable balloon).

[0184] I. Exemplary Blood Flow Control Devices

[0185] Figure 8Exemplary variations of a blood flow control device 804 are illustrated. The blood flow control device 804 may include: an elongated body 802; an expandable member 810 (e.g., a balloon) coupled to the elongated body 802 and configured for placement within a blood vessel (e.g., an aorta); and one or more sensors (e.g., 811a, 811b) coupled to (e.g., integrated with / integrated within) the shaft of the elongated body 802. The one or more sensors may be any sensor described herein (e.g., sensor 302, sensor chip 1120) and may be coupled to (e.g., integrated with / integrated within) the shaft of the elongated body in any suitable manner. For example, in some variations, the one or more sensors may be housed within a sensor housing and / or may be coupled to the elongated body via a sleeve. The blood flow control device 804 may be coupled to a controller 812 (e.g., controller 320, microcontroller chip 1130), which may be capable of being operably coupled to the one or more sensors and a pump (e.g., a syringe pump). In some variations, the controller 812 may alternatively be included in a chip having one or more sensors. A pump may be used to expand and contract the expandable member (e.g., to inflate and deflate the expandable member). In some variations, the blood flow control device may include multiple sensors, such as, for example, a first sensor proximal to the expandable member, a second sensor distal to the expandable member, and a third sensor located within the expandable member or otherwise configured to measure a parameter within the expandable member. In some variations, each of the multiple sensors may be configured to measure pressure (e.g., a proximal sensor may measure pressure proximal to the expandable member, a distal sensor may measure pressure distal to the expandable member, and an expandable member sensor may measure pressure within the expandable member).

[0186] A. Expandable Components

[0187] The expandable member 810 can be one of the following: disposed on, coupled to, integrated with, attached to, and / or attached to the shaft of the elongated body 802, and the size of the expandable member 810 can be controlled by a controller or a user. For example, the expandable member 810 can be configured to expand and contract and / or inflate and deflate so that the size (e.g., volume) of the expandable member 810 can change during use of the blood flow control device. During use, blood flow can be regulated or otherwise controlled by changing the size of the expandable member 810, thereby changing the area of ​​the blood vessel occluded by the expandable member 810. Fluids and / or compressed gases can be delivered through one or more lumens in the elongated body 802 to control and / or adjust the size (e.g., volume) of the expandable member 810. Thus, in some variations, expandable member 810 may be strategically placed within the patient's aorta, and the size of expandable member 810 may control blood flow through the patient's aorta, so that blood flow distal to expandable member 810 may be obstructed to enhance blood pressure proximal to expandable member 810. The outer surface of expandable member 810 may be configured to contact or otherwise dock with the wall of the patient's blood vessel (e.g., in the event of complete occlusion). Expandable member 810 may include any suitable elastomeric material (e.g., polyurethane, silicone, etc.). Alternatively, expandable member may include polyester, nylon, etc. In some variations, expandable member 810 may include shape memory material.

[0188] B. Sensor

[0189] The blood flow control device may include a sensor of any variation described herein. For example, in some variations, the blood flow control device may include one or more (e.g., two, three, four, or more) pressure sensors of any variation described herein, which are integrated into the elongated body 802. In some variations, the pressure sensor may be integrated into the elongated body 802 using a sleeve, as previously described herein. A distal sensor, whose location is indicated by reference numeral 811b, may be disposed between the tip of the elongated body 802 and the expandable member 810. A proximal sensor, whose location is indicated by reference numeral 811a, may be disposed between the base of the elongated body 802 (where the elongated body 802 is coupled to the device controller 812) and the expandable member 810. Each of the distal sensor and the proximal sensor may measure a physiological condition of the patient, such as physiological information indicative of blood flow through the aorta, to determine the patient's underlying physiological function.

[0190] In some variations, distal sensor 411b may be integrated proximally of expandable member 810, while proximal sensor 811a may be integrated distally of expandable member 810. For example, distal sensor 811b located proximally of expandable member 810 may be placed at a distance from expandable member 810 such that physiological data collected from distal sensor 811b may not be disrupted by blood flow downstream of expandable member 810. In some variations, distal sensor 811b may be placed at a distance between about 30 mm and about 10 mm, between about 25 mm and about 15 mm, between about 22 mm and about 18 mm from expandable member 810. For example, distal sensor 811b may be placed approximately 20 mm from expandable member 810. In some variations, the proximal sensor 811a located distal to the expandable member 810 may be positioned between about 30 mm and about 10 mm, between about 25 mm and about 15 mm, or between about 22 mm and about 18 mm from the expandable member. For example, the proximal sensor 811a may be positioned approximately 20 mm from the expandable member 810. As discussed above, in some variations, the sensor on the elongated body 402 may be positioned at a particular distance from the end of the expandable member 810 in order to obtain physiological data upstream and downstream of the expandable member 810.

[0191] Note that as used herein with respect to sensors and / or specific local blood pressure readings, the terms "proximal" and "distal" refer to the directionality of blood flow from the heart. That is, "proximal" is closer to the heart, while "distal" is farther from the heart. This should not be confused with the reverse usage of the terms when describing from the perspective of a medical device such as a catheter, where the "distal end" of the medical device would generally be understood as the end where the expandable element 810 is farthest from the device controller 812, and the "proximal end" would be understood as the end closer to the operator.

[0192] In some variations, the blood flow control device may further include an expandable member sensor ( Figure 8 802). For example, the expandable member sensor may be integrated with the expandable member 810 or integrated with the elongated body 802 within the expandable member 810. In variations in which the expandable member sensor is coupled to the elongated body 802, the sensor may be coupled to the elongated body 802 or integrated with the elongated body using any of the sensor integration configurations and / or structures described herein (e.g., sensor housings, sensor sleeves, etc.). In some variations, the expandable member sensor may be coupled to, integrated with, and / or disposed on a device controller 812, and may be fluidically coupled to the expandable member. The expandable member sensor may be any of the sensors described herein and may be configured to detect characteristics of the expandable member.

[0193] C. Controller

[0194] The blood flow control device 804 may include or may be coupled to one or more controllers. For example, the blood flow control device 804 may include a device controller 812 that may be coupled to a base of the elongated body 802. The device controller 812 may be communicatively coupled to one or more sensors, such as, for example, a proximal sensor, a distal sensor, and / or an expandable member sensor. For example, the device controller 812 may be electrically coupled to the proximal sensor, the distal sensor, and / or the expandable member sensor.

[0195] A blood flow control system may include a device coupled to a blood flow control device (e.g., Figure 8 A system controller of the blood flow control device 804). Fig.21 Exemplary variations of blood flow control system 2100 are illustrated. In some variations, in addition to device controller 2112 (e.g., Figure 8 In addition to the device controller 812 in the embodiment of the present invention, the blood flow control system 2100 may also include a system controller 2106. The system controller 2106 may be coupled to the blood flow control device 804, for example, via the device controller 2105, or in a variation without the device controller 2105, directly coupled to the blood flow control device via the elongated body 2102.

[0196] In some variations, the device controller 2105 may also include a position sensor that can be communicatively coupled to the pump 2108 (described further below). In some variations, the position sensor may measure the position of a portion of the pump 2108. For example, the position sensor may measure the position of the plunger of the syringe pump 2108. The position of this portion of the pump 2108 can be used to infer the amount of fluid that has been delivered to the expandable member 2110 and / or removed from the expandable member.

[0197] Additionally or alternatively, the device controller 2105 may include a motion sensor (e.g., an encoder, such as a magnetic encoder, an optical encoder, etc.) that can be communicatively coupled to the pump. If a motor is used to actuate the pump 2108, the encoder can monitor the movement of the motor, which can be used to determine the amount of inflation and / or deflation in the expandable member 2110. In some variations, the motion sensor can be a magnetic encoder. Additionally or alternatively, the motion sensor can be an optical encoder. Additionally or alternatively, at least a portion of the system controller 2106 may include an optical sensor and / or a contact sensor. The optical sensor and / or contact sensor may be capable of being operably coupled to a portion of the pump 2108 to determine the position of the pump 2108 and / or track the movement of the pump. The amount of inflation and / or deflation in the expandable member 2110 can be determined based on the position and / or movement of the pump 2108. In some variations, a flow sensor can be used to determine the amount of inflation and / or deflation in the expandable member 2110.

[0198] D. Pump

[0199] like Fig.21 As depicted, the blood flow control system 2100 may include a pump 2108 that may be operably coupled to the expandable member 2110 to facilitate adjusting the size thereof. The pump 2108 may be housed within a housing (e.g., within an open or closed cavity or chamber) of the device controller 2105 or the system controller 2106, or otherwise carried by the housing, or coupled to the housing, and may be communicatively coupled to one or both of the device controller 2105 and the system controller 2106. The pump 2108 may include or otherwise be coupled to an elongated member (e.g., tubing) including an inner lumen, which in turn may be coupled to an inner lumen (e.g., an inlet or inflation lumen) of the elongated body of the blood flow control device. In this manner, the pump 2108 may be in fluid communication with the expandable member 2110.

[0200] In some variations, the pump may be fluidly coupled to a valve (e.g., a stopcock) that may regulate the flow of fluid and / or compressed gas to the expandable member 2110. The size (e.g., volume) of the expandable member may be adjusted using the system controller 2106 and / or the device controller 2105 and the pump 2108.

[0201] The sensors described herein may be configured to measure one or more pressures (e.g., blood pressure, expandable member pressure) in order to determine a patient's physiological condition or state. A controller (e.g., a device controller and / or a system controller) communicatively coupled to the sensor may be configured to receive data from the sensor that may indicate the patient's physiological condition and / or pressure associated with the expandable member. The controller may compare the received data with target data and adjust the volume of the expandable member to achieve the target data.

[0202] II. Exemplary Pressure Measurement Devices

[0203] In some variations, any of the sensors described herein may be incorporated into an apparatus and / or system configured to monitor (e.g., alone, without additionally controlling blood flow) a patient's physiological condition or parameter (such as, for example, blood pressure). The sensors described herein may be placed in various arteries or veins to measure blood pressure, as mentioned above. In other cases, the sensor may measure temperature or another parameter in addition to blood pressure. The sensor may be placed, for example, in the aorta, internal carotid artery, pulmonary artery, subclavian artery, femoral artery, radial artery, brachial artery, vena cava, internal jugular vein, or subclavian vein. The sensor may be included on or otherwise positioned within an elongated body (e.g., a catheter) coupled to a controller.

[0204] Any sensor in the sensor described herein can be incorporated into a pressure measuring device. In some variations, the pressure measuring device may include a sensor (as described herein) located in a sensor housing, wherein the sensor housing is attached to an elongated body (e.g., a catheter) or otherwise integrated with the elongated body. The elongated body including the sensor located in the sensor housing can be directly introduced into the vascular system to measure pressure (e.g., blood pressure), or configured to be advanced through an existing arterial or venous line (e.g., a vascular access line). In some variations, the sensor can be assembled in a tubular housing (e.g., a hypotube or a catheter). The size of the sensor and the tubular housing can be set to allow the elongated body to be delivered to an artery or vein, or delivered through a vascular access line. The sensor can be formed to be physically small in size, such as about 0.1Fr to about 5Fr (including all values ​​and subranges therein), and in some cases, can be configured to be integrated into a tubular housing having a diameter ranging from about 0.1Fr to about 10Fr (including all values ​​and subranges therein). For example, the sensor can have a size of about 0.1 Fr, about 0.2 Fr, about 0.3 Fr, about 0.4 Fr, about 0.5 Fr, about 0.6 Fr, about 0.7 Fr, about 0.8 Fr, about 0.90 Fr, about 1 Fr, about 2 Fr, about 3 Fr, about 4 Fr, or about 5 Fr. The diameter of the tubular housing can be about 0.1 Fr, about 0.2 Fr, about 0.3 Fr, about 0.4 Fr, about 0.5 Fr, about 0.6 Fr, about 0.7 Fr, about 0.8 Fr, about 0.90 Fr, about 1 Fr, about 2 Fr, about 3 Fr, about 4 Fr, about 5 Fr, about 6 Fr, about 7 Fr, about 8 Fr, about 9 Fr, or about 10 Fr. The small size of the sensor may allow room to include other components of the pressure measuring device (e.g., reinforcing members, fluid lumens, etc.) in the elongated body. The size and / or diameter of the sensor and tubular housing will typically be selected based on the diameter of the elongated body, the vascular access line through which it will be advanced, and / or the bend angle of the artery or vein through which it will be passed. For example, when the elongated body is about 3Fr or 4Fr, the diameter of the sensor and / or tubular housing may be about 1Fr. The length of the tubular housing may range from about 5mm to about 15mm, including all values ​​and subranges therein. For example, the tubular housing length may be about 5mm, about 6mm, about 7mm, about 8mm, about 9mm, about 10mm, about 11mm, about 12mm, about 13mm, about 14mm, or about 15mm.

[0205] The sensor housing can be attached to the elongated body of the pressure measuring device in various ways. For example, the sensor housing can be attached using one or more structural components (e.g., struts) as previously described. The sensor and structural components can form a sensor assembly. For example, Fig. 20AAs shown, the sensor housing 2000 can be used to couple the sensor 2 to the elongated body 1. The sensor 2 can be encapsulated in a polymer layer in the sensor housing 2000 by placing the sensor 2 on a polymer layer (e.g., a layer including RTV silicone or a different polymer) and then curing the polymer. Next, the sensor 2 can be encapsulated by covering the sensor 2 with an additional polymer (e.g., RTV silicone) and then curing the polymer. The polymer can have a compliance that allows pressure signals to be transmitted through the polymer, so that physiological conditions such as, for example, blood pressure can be transmitted to the sensor 2 through the polymer. A separate seal 3 (e.g., an RTV silicone seal) can also be provided within the tubular sensor housing 2000 to protect the sensor 2 from pressurization. The sensor 2 and the sensor housing 2000 together (as a sensor assembly) can have a diameter sized to fit within the elongated body 1, and can be designed to have a small diameter (e.g., approximately 1 Fr). For example, as Fig. 20B As shown in the cross-sectional view of , the sensor housing 2000 in which the sensor 2 is disposed may have a size of about 1 Fr and may be included in an elongated body (e.g., catheter) 1 having a size of about 7 Fr. A pressure measurement device including a sensor of about 1 Fr and / or a sensor housing integrated into a 7 Fr catheter may be useful when the device is placed in the aorta to measure blood pressure therein.

[0206] A sensor used in a pressure measurement device may be connected to a printed circuit board assembly (PCBA) housing via one or more wires coupled to the sensor and one or more pins on the PCBA. Fig. 20A and Fig.22A , one or more conductors (e.g. Fig. 20A The wire 4 in the tube 6 can be disposed in the tube 6 and attached to the PCBA housing 7. The length of the tube 6 can be changed according to the vascular access site and the target location of the parameter to be measured (e.g., blood pressure) in the artery or vein. For example, the length of the tube can be in the range of about 35 cm to about 70 cm, including all values ​​and subranges therein. For example, the length of the tube can be about 35 cm, about 40 cm, about 45 cm, about 50 cm, about 55 cm, about 60 cm, about 65 cm, or about 70 cm.

[0207] The PCBA housing may be configured to connect to a controller (e.g., a controller of a blood flow control system) and may include a PCBA network configured to control one or more functions of the sensor. The PCBA housing may include a top portion and a bottom portion. The top portion and the bottom portion may be connected via a hinge or an adhesive, or may be attached by a snap fit, a friction fit, etc. The adhesive may be a strip of tape (e.g., a foam tape) on one or more areas on the bottom portion of the housing. Any suitable adhesive may be used. Reference Fig. 22BThe bottom portion 10 of the housing 7 may include double-sided foam tape 9 on two areas to adhere the bottom portion 10 to the top portion 11. The top portion 11 of the housing 7 may also include a layer of double-sided foam tape 9 for attaching components of the PCBA network 8 to the top portion. A coupler (e.g., silicone tubing) 12 may be included in the top portion 11 to attach tubing (e.g., silicone tubing) extending from the sensor. Fig.22A The PCBA housing 7 is connected to the tubing 6 in the PCBA housing 7, and the wires in the tubing 6 are connected to the PCBA network 8. In some variations, the PCBA housing 7 can also be attached to the patient's body using an adhesive. For example, the PCBA housing 7 can be provided on a patch having an adhesive surface configured to adhere the housing to a part of the patient's body, such as the skin of the patient's leg, arm, or torso.

[0208] Although the aforementioned variations have been described in more detail by way of illustration and example for the purpose of clarity and understanding, it will be apparent that certain changes and modifications may be practiced, and these changes and modifications are intended to fall within the scope of the appended claims. In addition, it should be understood that the components and features of the systems and devices described herein may be used in any combination. The description of certain elements or features of a particular drawing is not intended to be restrictive, nor should it be interpreted as implying that the element cannot be used in combination with any other described element. For all variations described herein, the steps of the method may not be performed in order. Some steps are optional, so that each step of the method may not be performed.

Claims

1. A sensor, comprising: a first circuit configured to receive an input clock signal and output a first output count signal at a predetermined sampling rate; a second circuit configured to receive the input clock signal and output a second count signal at the predetermined sampling rate; and A third circuit is coupled to the first circuit and the second circuit, and is configured to generate a third signal based on the first output count signal and the second output count signal. 2 . The sensor of claim 1 , wherein the first output count signal varies based on a first set of parameters, and the second output count signal varies based on a second set of parameters different from the first set of parameters. 3 . The sensor of claim 2 , wherein the first set of parameters includes one or more of temperature and voltage.

4. The sensor of claim 2, wherein the second set of parameters includes temperature, voltage, and one or more of the following: force, pressure, light amplitude, audio amplitude, radiation, and resistance or capacitance corresponding to a chemical or physical reaction.

5. The sensor of claim 1, wherein the third signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude. The sensor of claim 1 , wherein a frequency of the predetermined sampling rate is less than a frequency of the input clock signal.

7. The sensor of claim 1, wherein the first circuit comprises a first plurality of delay circuits arranged in a ring configuration, and the second circuit comprises a second plurality of delay circuits arranged in another ring configuration.

8. The sensor of claim 7, wherein the first plurality of delay circuits comprises a first plurality of inverter circuits, and the second plurality of delay circuits comprises a second plurality of inverter circuits, the second plurality of delay circuits being different from the first plurality of delay circuits. 9 . The sensor of claim 8 , wherein the first circuit comprises a first counter and a first latch, and the second circuit comprises a second counter and a second latch.

10. The sensor of claim 8, wherein the first plurality of inverter circuits are coupled to a first multiplexer and the second plurality of inverter circuits are coupled to a second multiplexer.

11. The sensor of claim 8, wherein the first plurality of inverter circuits and the second plurality of inverter circuits are in a closed loop configuration with positive feedback.

12. The sensor of claim 1, wherein the first delay circuit comprises a first resistor-capacitor delay circuit.

13. The sensor of claim 1, wherein the second circuit comprises one or more of a resistor-capacitor delay circuit, a resistor-inductor delay circuit, and a capacitive delay circuit.

14. The sensor of claim 1, wherein the first circuit comprises a first oscillator circuit and the second circuit comprises a second oscillator circuit.

15. The sensor according to claim 1, further comprising: a fourth circuit coupled to the third circuit, the fourth circuit being configured to receive the input clock signal and output a fourth count signal at the predetermined sampling rate, wherein the third circuit is configured to generate a fifth signal based on a difference between the first output count signal and the fourth output count signal.

16. The sensor of claim 15, wherein the fifth signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.

17. The sensor according to claim 1, further comprising: A substrate includes the first circuit, the second circuit, and the third circuit.

18. The sensor according to claim 1, further comprising: a first substrate, the first substrate comprising the first circuit and the second circuit; and A second substrate includes the third circuit.

19. The sensor of claim 1, further comprising: A fourth circuit is configured to output the third signal as a digital signal.

20. The sensor of claim 1, further comprising: A fourth circuit is configured to output the third signal as a set of binary coded bits at a periodic rate.

21. The sensor of claim 1, wherein the fourth circuit comprises one or more of a wire and an antenna.

22. A method for measuring a parameter, the method comprising: receiving an input clock signal; generating a first output count signal at a predetermined rate based on the input clock signal using a first circuit; generating a second count signal at the predetermined rate using a second circuit different from the first circuit; as well as A third signal is generated based on the first output count signal and the second output count signal.

23. The method of claim 22, wherein the first output count signal varies based on a first set of parameters and the second output count signal varies based on a second set of parameters different from the first set of parameters.

24. The method of claim 23, wherein the first set of parameters includes one or more of temperature and voltage.

25. The method of claim 23, wherein the second set of parameters includes temperature, voltage, and one or more of: force, pressure, light amplitude, audio amplitude, and resistance or capacitance corresponding to a chemical or physical reaction.

26. The method of claim 22, wherein the third signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, audio amplitude, and radiation.

27. The method of claim 22, wherein a frequency of the predetermined rate is less than a frequency of the input clock signal.

28. The method of claim 22, further comprising: using a fourth circuit to generate a fourth count signal at the predetermined rate; as well as A fifth signal is generated based on the first output count signal and the fourth output count signal.

29. The method of claim 28, wherein the fifth signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, audio amplitude, and radiation.

30. The method of claim 22, further comprising: The third signal is output as a digital signal.

31. The method of claim 22, further comprising: The third signal is output as a set of binary coded bits at a periodic rate.

32. A sensor, comprising: a first ring oscillator circuit that oscillates at a first oscillation rate based on a first set of physical parameters and a second set of physical parameters; a second ring oscillator circuit that oscillates at a second oscillation rate that is based on the first set of physical parameters but not on the second physical parameter; a first rate counter circuit operatively coupled to the first ring oscillator circuit and configured to count a number of first oscillations at the first ring oscillator circuit during a sampling period; a second rate counter circuit operatively coupled to the second ring oscillator circuit and configured to count a second number of oscillations at the second ring oscillator circuit during the sampling period; and A circuit system, the circuit system being configured to: receiving a representation of the first number of oscillations and a representation of the second number of oscillations, and In response to receiving the representation of the first number of oscillations and the representation of the second number of oscillations, a value associated with the second physical parameter at the sensor is generated based on the first number of oscillations and the second number of oscillations.

33. The sensor of claim 32, wherein the first set of physical parameters includes temperature and voltage, and the second physical parameter is pressure.

34. The sensor of claim 32, wherein the first ring oscillator circuit and the second ring oscillator are located on the same die.

35. A sensor, comprising: a first ring oscillator circuit that oscillates at a first oscillation rate based on a first set of physical parameters and a second set of physical parameters; a second ring oscillator circuit that oscillates at a second oscillation rate that is based on the first physical parameter but not on the second physical parameter; a first rate counter circuit operatively coupled to the first ring oscillator circuit and configured to count a number of first oscillations at the first ring oscillator circuit during a sampling period; a second rate counter circuit operatively coupled to the second ring oscillator circuit and configured to count a second number of oscillations at the second ring oscillator circuit during the sampling period; and A communication circuit system, wherein the communication circuit system is configured to: transmit the representation of the first oscillation quantity and the representation of the second oscillation quantity to a processing circuit system operatively coupled to the communication circuit system, so that the processing circuit system generates a value associated with the second physical parameter at the sensor based on the first oscillation quantity and the second oscillation quantity in response to receiving the representation of the first oscillation quantity and the representation of the second oscillation quantity from the communication circuit system.

36. The sensor of claim 35, wherein the first set of physical parameters includes temperature and voltage, and the second physical parameter is pressure.

37. The sensor of claim 35, wherein the first ring oscillator and the second ring oscillator are located on the same die.

38. A method comprising: obtaining a first count number indicative of a number of oscillations at a first ring oscillator circuit during a sampling period, the first ring oscillator circuit being associated with the sensor and oscillating at a first oscillation rate, the first oscillation rate being based on a first set of physical parameters and a second physical parameter; obtaining a second count number indicative of a number of oscillations at a second ring oscillator circuit during the sampling period, the second ring oscillator circuit being associated with the sensor and oscillating at a second oscillation rate, the second oscillation rate being based on the first physical parameter and independent of the second physical parameter; as well as A value associated with the second physical parameter at the sensor is determined based on the first count number and the second count number.

39. A sensor, comprising: a first circuit configured to receive an input clock signal and output a first output count signal at a predetermined rate; a second circuit configured to receive the input clock signal and output a second count signal at the predetermined rate; and A digital circuit is coupled to the first circuit and the second circuit, the digital circuit being configured to generate a digital signal based on the first output count signal and the second output count signal.

40. A sensor, comprising: a first circuit configured to receive an input clock signal and to output a first output clock signal with an adjustable delay, the first output clock signal having a predetermined ratio between the input clock signal and the first output clock signal; a second circuit configured to receive the input clock signal and output a second output clock signal using the adjustable delay; and A third circuit is coupled to the first circuit and the second circuit, and is configured to generate a third signal based on a difference between the first output clock signal and the second output clock signal.

41. The sensor of claim 40, wherein the first output clock signal varies based on a first set of parameters and the second output clock signal varies based on a second set of parameters different from the first set of parameters.

42. The sensor of claim 41, wherein the first set of parameters includes one or more of temperature and voltage.

43. The sensor of claim 41, wherein the second set of parameters includes temperature, voltage, and one or more of: force, pressure, light amplitude, audio amplitude, and resistance or capacitance corresponding to a chemical or physical reaction.

44. The sensor of claim 40, wherein the third signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.

45. The sensor of claim 40, wherein a frequency of the first output clock signal and a frequency of the second output clock signal are each greater than a frequency of the input clock signal.

46. ​​The sensor of claim 40, wherein the first circuit comprises a first plurality of delay circuits arranged in a ring configuration, and the second circuit comprises a second plurality of delay circuits arranged in another ring configuration.

47. The sensor of claim 46, wherein the first plurality of delay circuits comprises a first plurality of inverter circuits and a first adjustable delay circuit, and the second plurality of delay circuits comprises a second plurality of inverter circuits and a second adjustable delay circuit, the second plurality of delay circuits being different from the first plurality of delay circuits.

48. The sensor of claim 47, wherein the first adjustable delay circuit comprises a rate counter and the second adjustable delay circuit comprises a rate counter.

49. The sensor of claim 47, wherein the first plurality of inverter circuits are coupled to a first multiplexer and the second plurality of inverter circuits are coupled to a second multiplexer.

50. The sensor of claim 47, wherein the first plurality of inverter circuits and the second plurality of inverter circuits are in a closed loop configuration with positive feedback.

51. The sensor of claim 40, wherein the first delay circuit comprises a first resistor-capacitor delay circuit.

52. The sensor of claim 40, wherein the second circuit comprises one or more of a resistor-capacitor delay circuit, a resistor-inductor delay circuit, and a capacitive delay circuit.

53. The sensor of claim 40, wherein the first circuit comprises a first oscillator circuit and the second circuit comprises a second oscillator circuit.

54. The sensor of claim 40, further comprising: a fourth circuit coupled to the third circuit, the fourth circuit being configured to receive the input clock signal and output a fourth output clock signal using the adjustable delay, wherein the third circuit is configured to generate a fifth signal based on a difference between the first output clock signal and the fourth output clock signal.

55. The sensor of claim 54, wherein the fifth signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.

56. The sensor of claim 40, further comprising: A substrate includes the first circuit, the second circuit, and the third circuit.

57. The sensor of claim 40, further comprising: a first substrate, the first substrate comprising one of the first circuit and the second circuit; and A second substrate includes the other of the first circuit and the second circuit.

58. The sensor of claim 40, further comprising: A fourth circuit is configured to output the third signal as a digital signal.

59. The sensor of claim 40, further comprising: A fourth circuit is configured to output the third signal as a set of binary coded bits at a periodic rate.

60. The sensor of claim 40, wherein the fourth circuit comprises one or more of a wire and an antenna.

61. A method for measuring a parameter, the method comprising: receiving an input clock signal; generating a first output clock signal using an adjustable delay, the first output clock signal having a predetermined ratio between the input clock signal and the first output clock signal; generating a second output clock signal using the adjustable delay; as well as A third signal is generated based on a difference between the first output clock signal and the second output clock signal.

62. The method of claim 61, wherein the first output clock signal varies based on a first set of parameters and the second output clock signal varies based on a second set of parameters different from the first set of parameters.

63. The method of claim 62, wherein the first set of parameters includes one or more of temperature and voltage.

64. The method of claim 62, wherein the second set of parameters includes temperature, voltage, and one or more of: force, pressure, light amplitude, audio amplitude, and resistance or capacitance corresponding to a chemical or physical reaction.

65. The method of claim 61, wherein the third signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.

66. The method of claim 61, wherein a frequency of the first output clock signal and a frequency of the second output clock signal are each greater than a frequency of the input clock signal.

67. The method of claim 61, further comprising: generating a fourth output clock signal using the adjustable delay; as well as A fifth signal is generated based on a difference between the first output clock signal and the fourth output clock signal.

68. The method of claim 67, wherein the fifth signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.

69. The method of claim 61, further comprising: The third signal is output as a digital signal.

70. The method of claim 61, further comprising: The third signal is output as a set of binary coded bits at a periodic rate.

71. A sensor, comprising: a first circuit configured to receive an input clock signal and to output a first output clock signal with an adjustable delay, the first output clock signal having a predetermined ratio between the input clock signal and the first output clock signal; a second circuit configured to receive the input clock signal and output a second output clock signal using the adjustable delay; and A digital circuit is coupled to the first circuit and the second circuit, and is configured to generate a digital signal based on the first output clock signal and the second output clock signal.

72. The sensor of claim 71 , wherein the digital signal corresponds to a measurement parameter.

73. A device configured to monitor a physiological condition of a patient or to control blood flow in a patient, the device comprising: Slender body; The sensor of claim 1, 4, 8, 39, 40, or 71, coupled to the elongated body, wherein the sensor is configured to measure pressure; and A balloon is coupled to the elongated body and is configured for placement within a blood vessel.

74. The apparatus of claim 73, wherein the sensor is a distal sensor and wherein the distal sensor comprises a sensor of claim 1, 4, 8, 39, 40 or 71.

75. The apparatus of claim 73, wherein the sensor is housed within a sensor housing.

76. The apparatus of claim 75, wherein the sensor housing comprises a polymer.

77. The device of claim 76, wherein the sensor is encapsulated in the polymer.

78. The apparatus of claim 73, wherein the sensor housing is tubular in shape.

79. The apparatus of claim 73, further comprising: A sleeve is configured to couple the sensor housing to the elongated body.

80. A device configured to monitor blood pressure, the device comprising: Slender body; and A sensor disposed within a tubular sensor housing, the sensor comprising any of the sensors of claims 1, 4, 8, 39, 40, or 71, wherein the tubular sensor housing is coupled to the elongated body.

81. The apparatus of claim 80, wherein the sensor has a size ranging from about 0.1 Fr to about 5 Fr.

82. The apparatus of claim 81, wherein the sensor has a size of approximately 1 Fr.

83. The apparatus of claim 80, wherein the elongate body comprises a catheter configured to access an artery or a vein.

84. The apparatus of claim 83, wherein the artery is the aorta, the pulmonary artery, the internal carotid artery, the femoral artery, or the radial artery.

85. The device of claim 80, wherein the sensor is encapsulated in a polymer.

86. The device of claim 80, wherein the sensor is coupled to a PCBA housing.

87. The device of claim 86, wherein the PCBA housing comprises an adhesive configured to attach the PCBA housing to the patient's skin.

88. The device of claim 87, wherein the adhesive comprises an adhesive patch.

89. A method comprising: measuring a first value of a first parameter using a first sensor; sending the first value to a second sensor coupled to the first sensor; measuring a second value of a second parameter using the second sensor; as well as A serial value is generated including the first value and the second value.

90. The method of claim 89, wherein the serial value is a first serial, the method further comprising: sending the first serial value to a third sensor coupled to the second sensor; measuring a third value of a third parameter using the third sensor; as well as A second serial value is generated including the first serial value and the third value.

91. The method of claim 89, further comprising: The serial output is transmitted to a computing device, the computing device being configured to determine the first value and the second value based on the serial output.

92. The method of claim 89, wherein the first parameter and the second parameter are the same.

93. The method of claim 90, wherein the first parameter and the second parameter are different.

94. The method of claim 89, wherein the first sensor and the second sensor are operatively coupled to a computing device via only four signals, the four signals being a power signal, a clock signal, a ground signal, and an output signal.

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